JPH0212913A - Formation of metal or semiconductor electrode and wiring - Google Patents

Abstract

PURPOSE:To make dissociation and adsorption ability extremely high by utilizing the instability of gas on a particular transition element or an element capable of forming a d-band, said instability is due high ability of supplying electrons to th gas molecules from the underlying layer which is to grow selectively. CONSTITUTION:An element, whose outside electron configuration in the ground state is expressed as (n-1)d1-10ns0-2, (n: principal quantum number), or (n-2)f0-14(n-1)s<2>(n-1)p<6>, (n-1)d0-2ns<2>, (n: principal quantum number 6 or 7), or (n-1)d1-10ns0-2np0-6, (n: prindipal quantum number), is exposed in a portion on a substrate to greatly promote dissociation and adsorption of gas molecules of the surface supplied as raw material gas, so that surface reaction is facilitated to occur. A first SiO2 layer 6 is formed on a Si substrate 5, and after an Mo layer 7 is further formed on the SiO2 layer 6 by sputtering process etc., a second SiO2 layer 6 is formed thereon as a mask film to grow selectively. Then, a patterning substrate exposing the under Mo layer 7 is obtained. When hydrogen gas and WF6 gas are introduced onto this substrate, W grows selectively only on the underlying Mo layer within a through hole.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for forming metal or semiconductor electrodes and wiring, and specifically, a method for selectively forming a semiconductor or metal on a part of the surface of a substrate. It's about how to do it.

[Prior Art] Conventionally, in the formation of electrodes and interconnections of a semiconductor device, the method shown in FIG. 7 (
As shown in a), an insulating layer 2 having an opening (through hole 3) is formed on the lower electrode/wiring layer i, and then a metal layer such as AX, Mo, etc. is formed by sputtering or vacuum evaporation. However, with the miniaturization of semiconductor devices, the diameter of the through hole 3 becomes minute and the aspect ratio becomes higher.
As shown in C), metal was not deposited on the side wall of the through hole 3, causing a problem that sufficient connection with the lower electrode/wiring layer could not be established.

In order to improve this, a selective growth method using chemical vapor deposition (CVD) has been proposed as an alternative to the conventional sputtering method and vacuum evaporation method. In this method, a film is grown only inside the through hole 3 by using the surface reaction of a gas whose constituent element is the element that fills the through hole 3 portion, and no film is formed on the mask wA (insulating layer 2). It is characterized by Methods that allow this selective growth are already known, such as the method of selectively growing a metal using a metal fluoride such as tungsten hexafluoride (WFa) and hydrogen (H3), or the method using tetrachlorogermane (GeCJ14) and hydrogen. A method for selectively growing Ge using
-179113) etc. have been proposed.

These methods utilize the difference in the ease with which surface reactions occur between the base inside the through hole 3 and the insulating layer 2 used as a mask. In other words, by taking advantage of the fact that the hydrogen reduction reaction of the raw material gas occurs more easily on the underlying surface than on the insulating layer 2, the element constituting the raw material gas (W in the former, W in the latter) is preferentially transferred inside the through hole. Ge).

[Problem to be solved by the invention] Conventionally, St.
, Al2. Ge or the like is generally used.

However, when selective growth is performed on these bases by the method described above, the following problems arise.

■The base material is etched by the raw material gas (WF, GeCfL4). (The base is Si or Ge) ■ It is difficult to ensure selectivity, so there is little latitude in the conditions for ensuring selectivity. (The base is St.

Ge, Al2) ■The larger the exposed area of the base, the worse the selectivity.

(When the base is St or Ge) As a method for solving these problems, the following proposals have been made.

(2) In the selective growth of W using wFs, a method has been proposed in which S i H4 is introduced together with WF6 and WF6 is actively reduced in order to prevent the above-mentioned etching of the underlying layer.

This method has the advantage of preventing etching of the underlying layer and increasing the speed of film formation. However, in this method, another problem arises in that SiH is deposited on the mask film due to thermal decomposition of itself, which deteriorates the selectivity of W growth.

One possible way to solve this problem is to set the deposition temperature low in order to suppress the thermal decomposition reaction of SiH4. However, deposition of St cannot be completely eliminated even at room temperature, and W itself cannot be expected to have the effect of sweeping out impurities (oxygen) at high temperatures, so a good W film cannot be obtained. Furthermore, there is a drawback that the adhesion between the deposited W and the base is poor. Moreover, this method has the disadvantage that the grown film contains St in W, and therefore cannot be a film with essentially the same low resistance as W.

■If the base is Si, in order to prevent the above-mentioned etching of the base, a method is proposed in which the temperature is set at a low temperature at the beginning of film formation, and then the temperature is raised once W starts to grow by - degrees to continue growing W. has been done. However, this method involves a two-step growth method, so there is a problem that the W deposition process becomes complicated.

[Means for Solving the Problems] The present invention provides that the outer electron configuration in the ground state is; (n-1
) dIAIIOnSOA12 (n, principal quantum number) or: (n-2)f0~”(n-1)s2 (n-1)p'(
n-1) d0~' n52 (n: principal quantum number 6 or 7) or; (n-1) dl#1Ons0~2 npOtv6
(n: principal quantum number) a step of exposing an element expressed as (n: principal quantum number) on a part of the substrate;
A metal characterized by comprising a step of introducing molecules having at least metal atoms or semiconductor atoms as constituent elements to form a metal layer made of the above-mentioned metal atoms or a semiconductor layer made of semiconductor atoms only on the exposed surface. There are gist in methods for growing thin films and semiconductor thin films.

[Function] According to the present invention, by significantly promoting the dissociation and adsorption of gas molecules supplied as a raw material gas on the surface, surface reactions are facilitated.
The problem that arises when using Si as a base using the system is to eliminate the dependence of the offset selectivity on the exposed area of the base until etching of the base or film formation begins, or to eliminate poor selectivity when using All as the base. It is possible to prevent offsets until film formation. Furthermore, since the deposition temperature can be raised to a high temperature, the adhesion to the base is also improved.

[Example 1 (Example 1) First, a case will be described in which W is selectively grown in a desired region using WF and H2. FIG. 1 is a process sectional view for explaining this embodiment.

First, a first 5in2 layer 6 is formed on the St substrate 5, and then M is formed by a known sputtering method or the like.

After forming layer 7, a second 5i02 layer 6 is formed thereon as a mask film for selective growth (119th (a)).
. Thereafter, patterning is performed by photolithography and etching to obtain a patterned substrate (FIG. 2(b)) in which the underlying Mo layer 7 is exposed. On this substrate, hydrogen gas and WFs gas were applied at a substrate temperature of 460°C, hydrogen gas 18QOsccm, WF, and gas 10105e.

Total pressure 0. When introduced as tai'orr, W can be selectively grown only on the Mo substrate inside the through hole with a W growth rate of 800 people/min. At this time, the selective growth became as shown in FIG. 2, and there was no erosion of the base. Furthermore, FIG. 3 shows the measurement results of the dependence of the W grown film thickness on the deposition time, and it was shown that the W grown film thickness was proportional to the deposition time, and no offset occurred during film formation.

In addition, in this example, the through hole diameter is 0.8 μm1
The aspect ratio was approximately 1.2, but the through hole diameter was 0.
．． It was also confirmed that even when the aspect ratio was 5 μm and 2.0, the deposition rate did not change at all and that sufficient selectivity could be ensured.

In addition, M
Pattern O as shown in Figure 4 (approximately 1/1/2 of the total area).
2) Even when W was deposited in this manner, W could still be grown with good selectivity. As a result, it was found that no deterioration in selectivity occurred even when the underlying exposed area was large.

As shown above, when the exposed part of the base is Mo, there is no erosion of the base on this Mo, there is no offset in film formation, and furthermore, it is possible to selectively grow W without depending on the exposed area of the base. did it. The reason is shown below.

The reason why W can be selectively grown by introducing WF and H2 onto the substrate is due to the difference in the reaction rate of the surface chemical reaction of WF and H2 on the exposed portion of the underlying substrate and on the mask film. If the reaction does not involve the surface, a reduction reaction of WF will occur in the gas phase, and selective growth will not be possible. Therefore, it is clear that the reduction reaction of WF6 occurs on the surface. At this time, in order to reduce at least WF6, H2 must be dissociated and adsorbed on the surface (dissociation adsorption).
and chemically active hydride complexes (hydride c
o+nplex). At this time H3
The process of dissociation and adsorption of is explained as follows.

In other words, as H2 approaches the surface, Fig. 5(a)
The bonding orbital and antibonding orbital of H2, which were separated as in
As shown in FIG. 5(b), the state density distributions are superimposed on both sides of the Fermi level. As a result, H2
Electrons flow into the antibonding orbital of the molecule from the underlying substrate side and H2
The molecule is destabilized. As you get closer to the surface,
Eventually, hydrogen forms bonds with surface atoms, forming bonding and antibonding orbitals with the surface atoms as shown in FIG. 5(C). The above is a qualitative explanation of the dissociative adsorption of H2 on the surface.

The above tendency increases significantly in transition metals having d electrons. This is because the flow of electrons from H2 into the d vacant orbital of the transition metal and back donation, that is, the flow of dπ electrons of the transition metal into the H2 antibonding orbital, are extremely likely to occur. As mentioned above, since dissociative adsorption of H2 is extremely likely to occur on transition metals, W
When F6 and H2 are introduced, H2 is quickly dissociated and adsorbed at the exposed portion of the Mo base to form a Mo hydride complex, and the reduction reaction of W Fa is immediately initiated. Therefore, there is no etching of the substrate and no offset of deposition.
W can be selectively grown on the MO exposed portions.

On the other hand, when the exposed base is Si, since St does not have d electrons, it has a low ability to dissociate and adsorb H2. Therefore, on Si, first, WF6 +3/2 S i =W+372 S i F
W is deposited on the exposed portion of St by the St reduction reaction 4. When - degree W is deposited, since W itself is a transition metal, dissociative adsorption of H2 occurs on the deposited W, and a W hydride complex is formed. As a result, reduction of WF6 is promoted and W deposition occurs.

For the above reasons, when the exposed base is made of Si, the base St must be etched in order to form a W film.

Further, SiF4 produced in the above reaction produces SiF2 as a fragment thereof. SiF2 undergoes the following reaction (J, Am, Chen+, Soc, 87, 282
4 (1965)) to produce higher silanes such as disilane. Since high-grade silane easily deposits on the mask film as Si by thermal decomposition, this serves as a nucleus and W is deposited on the mask film as well, causing a deterioration of selectivity.

The reason why the selectivity depends on the Si exposed area is because of the above reason, when the St exposed area is large, the Si
This is because the concentration of F increases, resulting in an increase in the concentration of higher silane on the mask film. Therefore, if the base is made of a transition metal such as MO, it becomes SiF.

Since there is no generation of , the dependence of selectivity on the exposed area of the substrate disappears.

In addition, when AIL is used as a base, valence electrons exist as free electrons in AJI, so there is no ability to pour electrons into the antibonding orbital of H2, but since it is not a transition metal with d electrons, the above example Compared to the MO shown above, the ability to dissociate and adsorb H2 is significantly inferior. Therefore, when using A°C as a base, it is difficult to ensure selectivity.

In the above embodiment, a Si film deposited by ECR was used as the mask film, but it has been confirmed that the mask film may be a thermal oxide film, a sputter oxide film, or a CVD oxide film.

In addition, the exposed base may be a transition metal or a base containing a transition metal in addition to Mo, such as MO silicide, Ti, or Ti.
It has been confirmed that silicide, W, and W silicide may also be used.

What should be noted here is that the dissociative adsorption of H2 depends on the ability of the underlying transition metal to supply electrons to the antibonding orbital of H2. Therefore, when using a transition metal compound as a base, compounds with strong ionic bonds, such as T
In the case of iN, the d electrons of Ti are attracted to the nitrogen side, so the electron supply ability becomes low and W does not grow.

(Example 2) Next, an example of selectively growing Ge using GeCu4 and H2 will be described. G e Cj2 G by a and H2
The a film growth is due to the Langmier-Hinge-Elwood process that involves dissociative adsorption of G e Cfl 4 and H2, and the detailed reaction process has been published by the present inventors (Fangben, Takahashi, 34th. Joint Conference on Applied Physics (1987) Proceedings Volume 1, P133, 28a
-ZC-5).

In this system, when Si is used as the base substrate, Ge is not formed on SiO2 used as a mask film, but Ge is also not formed on Si. This is because SL has d electrons. This is because the dissociative adsorption of H2 necessary for the Langmuir-Hinge-Elwood process does not occur. On the other hand, when Ge is used as a base, a Ge film is formed on Ge. This is because although Ge is not a transition metal,
This is because, unlike Si, it has 3d electrons, so it has a high ability to supply electrons to H2, and H2 is easily dissociated and adsorbed on the Ge surface.

Therefore, this fact and GeCJZ4-H.

Since Ge film formation in this system occurs through the Langmier-Hinge-Elwood process, it can be seen that when Ge is selectively grown in a GaCl2-H2 system, the effects of the present invention can be obtained even when Ge is used as a base. It can also be seen that a transition metal can be used as a base in the same manner.

Note that GeH4, GeH2 (CH3).

GeH2(Cz Hs L2*Aj!(CHs)s
eAft(C2H1l)! , AL (Cs H7)
It has been known that 3Si, H, etc. can be selectively grown using an insulating film such as 5i02 as a mask film, but if the surface containing the transition metal is exposed in the exposed part of the base, it can be easily selected for the above reasons. It is clear that sex can be ensured.

In the above examples, a system containing a transition metal was used as the substrate, but it is also possible to selectively grow the transition metal on the substrate by exposing the transition metal to the surface by ion implantation or a focused ion beam. The good news is obvious. Next, this method will be described as Example 3.

(Example 3) In this example, a method for forming metal wiring on a substrate according to the present invention will be described. FIG. 6 is a process sectional view for explaining this embodiment.

First, a 5i02 film 6 is formed on the SL substrate 5, and a desired mask pattern is formed (FIG. 6(a)).
d Cj! A Pd implantation layer is formed by a known metal implantation method using x gas, the resist serving as a mask material is removed, and a surface modified layer is formed by patterning Pd on the surface (see Fig. 7 (b). ), L, When CVD of W is then performed under the same conditions as the W selective growth method described above, W is selectively grown only on the surface modified layer by Pd, as shown in Figure 7(C). can be done.

In this example, Pd was used as a transition metal on the surface, and selective growth of W was made possible by significantly promoting the dissociation and adsorption of hydrogen on this surface-modified layer, and a W wiring pattern was obtained.

Of course, the transition metal for forming the surface modified layer may be any metal as long as the molecules composed of the transition metal atoms can be gasified. For example, T i Cj!
a, WFa, W(CO)a.

Mo Fa, Mo (Co) a, Ni
Of course, it is possible to use (CO) a and the like.

As a method for forming the surface-modified layer using a transition metal, it goes without saying that in addition to the metal implantation method described above, a metal supporting method commonly used in catalyst chemistry may be used.

As described above in Examples 1.2 and 3, the selective growth phenomenon occurs on surfaces that have a high ability to flow electrons particularly into antibonding orbitals among the molecular orbitals constituting hydrogen molecules. Such ability means that the outer electron configuration of the ground state is (n-1)dlA'1Ons0~2 (n, principal quantum number) or (n-2)f'~"(n-1)s" (n- 1) p'
(n-1) In transition metals represented by d'~2ns2 (n: principal quantum number 6 or 7), it is noticeable because the so-called ability to transfer and donate electrons to the 2π1 antibonding orbital of the hydrogen molecule is high. be able to. However, as can be easily understood by those skilled in the art, the donor ability of transition metals is due to the difference in ligand field splitting due to the approach of hydrogen molecules of transition metal atoms, or the higher S of d and f electrons. It should be noted that there are exceptional surfaces where, for example, on Au surfaces, dissociative adsorption of H3 does not occur, and therefore W cannot grow, because it is affected by the electronic state such as screening by electrons and p electrons, or by the surface atomic structure. It goes without saying that it should be done.

In addition, even if it is not a transition metal, an element with a base electron configuration of (n-1)d'~10nsO, -2npO~6 (n: principal quantum number) that can form a-bind, such as Ge, As mentioned above, since H2 can be dissociated and adsorbed, selective growth can be performed thereon.

In addition to the transition metals and Ge mentioned above, on systems with free electrons in the valence band, such as metals such as Aβ, the dissociative adsorption ability of <82 is significantly inferior to that of d-electron series elements.
By introducing a large amount of hydrogen into the surface and bringing it into contact with the surface, the equilibrium can be shifted in the direction of dissociative adsorption and dissociated hydrogen can be formed on the surface, thereby enabling selective growth.

The base for selective growth of W using WF6 and H2, which are relatively commonly used in LSI processes, can be described as follows based on the above-mentioned principle.

Mo, W>MoSi,,WSi,,TiSi.

＞Ge＞＞An＞n” −S i >S i >P”
-Si Note that the structure of the surface exposed to the gas phase for selective growth may be such that the entire surface of the base is made of the above-mentioned material and a mask film is formed to form an opening, or a so-called multilayer structure in the LSI process is used. It is also possible to form a multilayer structure like a via hole for wiring, and open it on a layer made of the above-mentioned material system.Furthermore, as already mentioned,
It goes without saying that surface treatment or surface modification may be performed to form a portion made of the above-mentioned material system on the surface, and selective growth may be performed thereon, as long as the spirit of the present invention is not impaired. Of course, there are many ways to configure the surfaces exposed to the gas phase.

[Effect of the invention] As explained above, the outer electron configuration in the ground state is; ~”(n-1)s'(n-1)p'
(n-1) d'~2 n s 2 (n: principal quantum number 6 or 7); or; (fi-i) dl''1 (InsOS2 npO~6
(n: principal quantum number) Elements that can form d-bind have a high ability to supply electrons to the underlying gas molecules on which selective growth is to be performed, so they cannot destabilize the gas molecules. It is characterized by extremely high dissociative adsorption capacity.

Therefore, when selective growth is performed, if the above-mentioned atoms are present on the substrate on which selective growth is to be performed, their dissociative adsorption ability will not etch the substrate and will not cause offset, resulting in good selectivity. Selective growth can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing through-hole filling by the conventional method, FIG. 2 is a diagram showing the substrate forming process in Example 1, FIG. 3 is a diagram in which W is buried in the through-hole in Example 1, and FIG. 5 shows the time dependence of the W growth film thickness in Example 1, FIG. 5 shows the pattern on the substrate used to examine the area dependence of selectivity in Example 1, and FIG. Diagram 7 explaining the principle of dissociative adsorption of molecules on a surface
The figure shows a method of forming a wiring pattern using selective growth of W on a Pd implanted layer. 1... Lower electrode wiring layer 3... Through hole 5... Si base layer 7... Mo layer 9... Resist 2... Insulating layer (mask@) 4... Metal layer 6... 5i02 layer 8・ψ9W 10... Pd surface modified layer (1 mf at the time of deposition)

Claims (1)

[Claims] The outer electron configuration in the ground state is; (n-1)d^1^~^1^0ns^0^~^2(n:
(principal quantum number) or; (n-2)f^0^~^1^4(n-1)s^2(n-
1) p^6 (n-1) d^0^~^2ns^2 (n: principal quantum number 6 or 7) Or; (n-1) d^1^~^1^0ns^0^~^ 2np^
a step of exposing an element expressed as 0^ to ^6 (n: principal quantum number) on a part of the substrate;
A metal characterized by comprising a step of introducing molecules having at least metal atoms or semiconductor atoms as constituent elements to form a metal layer made of the above-mentioned metal atoms or a semiconductor layer made of semiconductor atoms only on the exposed surface. Or a semiconductor electrode/wiring formation method.