JP2003303785A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device wherein a thin film containing aluminum can properly be embedded in a contact hole which is formed in a semiconductor substrate and has a small width and diameter and a large aspect ratio. <P>SOLUTION: A polysilicon film 15 is formed on the surface of a silicon substrate 1 having a trench 4 by a CVD method. An aluminium thin film 16 is formed on the surface of the silicon substrate 1 by a sputter method while the silicon substrate 1 is heated. The ratio of the amount of silicon which is supplied to the silicon substrate 1 by the CVD method to the amount of aluminum which is supplied to the silicon substrate 1 by the sputter method can be made, e.g. at least 0.1 at.% and 1 at.%. <P>COPYRIGHT: (C)2004,JPO

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 such as a MOS FET, and more particularly to forming a thin film containing aluminum so as to fill a fine contact hole formed on a semiconductor substrate such as a silicon substrate. The present invention relates to a method for manufacturing a semiconductor device including steps.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device, an electrode thin film made of aluminum is formed so as to fill a fine hole-shaped or trench-shaped contact hole formed on a silicon substrate. Such an electrode thin film serves as an extraction electrode of an element (for example, a transistor) formed on a silicon substrate. Such a thin film is
Conventionally, it has been formed by supplying aluminum atoms onto a silicon substrate by a sputtering method to form an aluminum thin film so as to fill the contact hole.

[0003]

However, with the recent miniaturization of wiring patterns, the width and diameter of contact holes have become smaller (for example, 0.6 μm or less). On the other hand, the depth of the contact hole hardly changes even if the wiring pattern is miniaturized, so that the ratio (aspect ratio) of the depth of the contact hole to the width or diameter of the contact hole becomes large (for example, 1 or more). .

In the contact hole having such a small width and diameter and a large aspect ratio, the aluminum thin film which can satisfactorily fill the contact hole could not be formed by the above method. Specifically, there is a problem that voids (voids) are formed in the aluminum thin film at the portions corresponding to the contact holes. This is because in the sputtering method, the aluminum thin film grows so as to block the opening of the contact hole before the inner space of the contact hole having a small width and diameter and a large aspect ratio is completely filled with aluminum atoms. .

Further, there is a problem that aluminum atoms are diffused (aluminum spikes) from an aluminum thin film to a diffusion region on a silicon substrate or the like at the time of film formation or a subsequent step, and the pn junction of the element is destroyed. . Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor device capable of satisfactorily embedding a thin film containing aluminum in a contact hole formed on a semiconductor substrate with a small width and diameter and a large aspect ratio. .

Another object of the present invention is to provide a method of manufacturing a semiconductor device in which aluminum atoms are less likely to diffuse from a thin film containing aluminum buried in a contact hole.

[0007]

[Means for Solving the Problems and Effects of the Invention] According to the invention of claim 1 for solving the above problems, aluminum is filled so as to fill the contact hole (4) formed on the semiconductor substrate (1). A method of manufacturing a semiconductor device, comprising forming a thin film (11) containing silicon, comprising: a base film forming step of forming a silicon containing thin film (15) on an inner surface of the contact hole; An aluminum thin film forming step of forming a thin film (11, 16) containing aluminum on the surface of the semiconductor substrate so as to fill the contact hole while heating the semiconductor substrate. Is.

The alphanumeric characters in the parentheses indicate corresponding constituent elements in the embodiments described later. The same applies in this section below. According to this invention, prior to the formation of a thin film containing aluminum (hereinafter referred to as “aluminum thin film”), a thin film containing silicon (base layer) is formed on the surface of the semiconductor substrate including the inner surfaces of the contact holes. . In the subsequent aluminum thin film forming step, for example, aluminum atoms supplied onto the semiconductor substrate by the physical vapor deposition method do not easily reach the inside (particularly the inner wall) of the contact hole on the semiconductor substrate. However, aluminum atoms that have reached portions other than the contact holes on the surface of the semiconductor substrate can move into the contact holes while diffusing into the base film. Therefore, a part of the thin film formed by depositing aluminum atoms on the portion of the semiconductor substrate outside the contact hole moves so as to flow into the contact hole along the inner surface of the contact hole.

As a result, the inside of the contact hole is filled well and an aluminum thin film grows. In particular, when the contact hole has a narrow width or diameter of 0.6 μm or less and an aspect ratio of 1 or more, such a manufacturing method is effective. The unnecessary part of the aluminum thin film is then
You may remove by etching etc. In this way, an aluminum thin film well embedded in the contact hole can be formed, and for example, the semiconductor layer (which may be the substrate itself) exposed on the inner surface of the contact hole is electrically connected to the aluminum thin film. it can.

When the aluminum thin film grows, silicon atoms diffuse from the underlayer to the aluminum thin film. Therefore, the aluminum thin film contains silicon. As a result, aluminum atoms in the aluminum thin film are less likely to diffuse into the semiconductor layer exposed on the inner surface of the contact hole (particularly, one made of silicon), which causes p formed inside the semiconductor layer.
It is possible to prevent the destruction of the n-junction.

The semiconductor substrate may be, for example, a silicon substrate. The contact hole may be formed in the film formed on the semiconductor substrate.
According to a second aspect of the invention, the ratio of the amount of silicon supplied to the semiconductor substrate in the base film forming step to the amount of aluminum supplied to the semiconductor substrate in the aluminum thin film forming step is 0.1% in atomic ratio. It is above and 1% or less, It is a manufacturing method of the semiconductor device according to claim 1 characterized by things.

As a result, the migration of aluminum atoms due to the diffusion described above effectively occurs, and the aluminum thin film can be satisfactorily embedded in the contact hole. It is also possible to prevent the generation of silicon nodules due to excess silicon. The invention according to claim 3 is characterized in that the underlying film forming step includes a step of forming a polysilicon thin film (15) by a chemical vapor deposition method.
It is a manufacturing method of the semiconductor device described.

By the chemical vapor deposition method, a polysilicon film (base film) can be uniformly formed inside the contact hole (inner wall or the like). The aluminum thin film can be formed by, for example, the sputtering method, which is an example of the physical vapor deposition method. The invention according to claim 5 is characterized in that the aluminum thin film forming step includes the step of heating the semiconductor substrate to 300 ° C. to 400 ° C. Is the way.

By heating the semiconductor substrate to 300 ° C. or higher in the aluminum thin film forming step, the above-mentioned diffusion of aluminum atoms and silicon atoms can be suitably caused, and the aluminum thin film can be satisfactorily embedded in the contact hole. In addition, the heating temperature of the semiconductor substrate is set to 4
By setting the temperature to 00 ° C. or less, diffusion of aluminum atoms from the aluminum thin film embedded in the contact hole to the semiconductor substrate or the like can be reduced.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, referring to the accompanying drawings,
Embodiments of the present invention will be described in detail. Figure 1
MOS FET manufactured by applying the manufacturing method of the present invention
(Metal Oxide Semiconductor Field Effect Transisto
It is a schematic sectional drawing which shows the structure of r).

An n ⁻ type epitaxial layer 2 is formed on the surface layer of the silicon substrate 1. A plurality of ridge-shaped laminated films 3 are arranged in parallel on the epitaxial layer 2. Between the adjacent laminated films 3 are holes 4. The laminated film 3 includes a p ⁻ layer 5, an n ⁺ layer 6, and a silicon oxide layer 7, which are laminated from the lower portion (epitaxial layer 2 side) toward the upper portion.
Inside each laminated film 3, a polysilicon layer 8 extending from the upper part of the epitaxial layer 2 is formed. The polysilicon layer 8 penetrates the p ⁻ layer 5 and the n ⁺ layer 6 and is in contact with the silicon oxide layer 7 on the upper side (the side opposite to the epitaxial layer 2 side). The polysilicon layer 8 is made conductive by addition of impurities, and is exposed to the outside in a direction parallel to the length direction of the laminated film 3 (direction perpendicular to the paper surface in FIG. 1), and the gate electrode of the FET. It is supposed to function as.

An oxide film 9 is formed around the polysilicon layer 8 except for the portion in contact with the silicon oxide layer 7. Between the p ⁻ layers 5 of the adjacent laminated films 3, the p ⁺ layer 1 having a smaller thickness than the p ⁻ layer 5 is formed in a portion in contact with the epitaxial layer 2.
0 is formed. An aluminum electrode film 11 containing aluminum (Al) as a main component is formed on the laminated film 3 and the p ⁺ layer 10 so as to fill the hole 4. The aluminum electrode film 11 contains a small amount (for example, 0.3% in atomic ratio with respect to aluminum) of silicon. The aluminum electrode film 11 functions as an extraction electrode for the n ⁺ layer 6.

In the MOS FET having the above structure, the width W1 of the hole 4 is, for example, 0.6 μm, and the ratio of the depth D to the width W1 of the hole 4 (aspect ratio) D / W1 is large (for example, 1 or more). The width W2 of the polysilicon layer 8 is, for example, 0.6 μm, and the width W3 of a portion of the laminated film 3 existing on one side of the polysilicon layer 8 is, for example, 0.45 μm. Therefore, the width W4 of the element unit of this MOS FET is, for example, 2.1 μm.

FIG. 2 is a schematic sectional view for explaining the forming process of the aluminum electrode film 11. First, p ⁺
CVD is performed on the layer 10 and the laminated film 3 (silicon substrate 1).
The polysilicon film 15 is formed by the (chemical vapor deposition) method (FIG. 2A). The polysilicon film 15 is formed with a uniform thickness on the epitaxial layer 2, the side surface of the laminated film 3 (inner wall of the hole 4), the upper surface of the laminated film 3, and the like. The thickness of the polysilicon film 15 can be set to 100 Å, for example.

Next, in this way, the polysilicon film 15 is formed.
Aluminum atoms are deposited by a sputtering method on the silicon substrate 1 on which the aluminum thin film 1 has been formed.
6 is formed (FIGS. 2B to 2D). At this time, the silicon substrate 1 is heated. Since aluminum atoms supplied onto the silicon substrate 1 by the sputtering method do not easily reach the inside of the holes 4, the aluminum atoms are mainly deposited outside the holes 4 to form the aluminum thin film 16 at the beginning of film formation. Form. Since aluminum atoms diffuse into the polysilicon film 15, a part of the aluminum thin film 16 formed outside the hole 4 moves so as to flow into the hole 4 (FIG. 2B).

The silicon atoms forming the polysilicon film 15 also diffuse into the aluminum thin film 16. In this way, the holes 4 are gradually filled with the aluminum thin film 16 (FIG. 2C), and the holes 4 are completely filled with the aluminum thin film 16 at the end of the film formation.
After stopping the supply of aluminum atoms to the silicon substrate 1, the heating of the silicon substrate 1 may be continued for an appropriate time. In the above steps (FIGS. 2A to 2D), the ratio of the amount of silicon to the amount of aluminum supplied to the silicon substrate 1 is the amount of aluminum to the aluminum at the heating temperature of the silicon substrate 1 in the step of forming the polysilicon film 15. It is preferably within the solid solution limit of silicon. In this case, all the silicon atoms forming the polysilicon layer 8 move into the aluminum thin film 16, and the aluminum thin film 1
After the film formation of 6, the polysilicon layer 8 does not exist between the aluminum thin film 16 (aluminum electrode film 11) and the p ⁺ layer 10 and the laminated film 3.

In this way, a good aluminum electrode film 11 without voids (voids) is obtained (FIG. 2).
(D)). In particular, when the hole 4 has a narrow width or diameter of 0.6 μm or less and an aspect ratio of 1 or more, such a manufacturing method is effective. The aluminum electrode film 11 contains aluminum as a main component and a small amount of silicon (for example, 0.3% in atomic ratio to aluminum). After the aluminum electrode film 11 is formed, unnecessary portions of the aluminum electrode film 11 are removed by etching or the like.

Since the aluminum electrode film 11 contains silicon within the solid solution limit, even when the silicon substrate 1 is heated to a high temperature during the formation of the aluminum electrode film 11 by the sputtering method or in other steps, Aluminum atoms forming the aluminum electrode film 11 are less likely to diffuse into the p ⁺ layer 10, the laminated film 3, the epitaxial layer 2, and the like. Therefore, the epitaxial layer 2 constituting the device,
Aluminum atoms will not diffuse into the p ⁻ layer 5 and the n ⁺ layer 6 to destroy the pn junction.

In the method of forming the aluminum electrode film 11, it is not necessary to form the barrier metal layer before forming the aluminum electrode film 11. Although one embodiment of the present invention has been described above, the present invention can be implemented in other forms. For example, the manufacturing method according to the present invention can also be applied to the case where a thin film is formed by filling various contact holes of a semiconductor device other than a MOS FET.

For example, in the above embodiment, the aluminum electrode film 11 is formed so as to be electrically connected to the p ⁻ layer 5 (semiconductor layer) exposed on the side surface of the hole 4 (contact hole). It may be formed so as to be electrically connected to the semiconductor layer (including the substrate itself) exposed on the bottom surface of the hole. In this case, only the insulator may be exposed on the inner wall of the contact hole. Further, the aluminum electrode film 11 may be electrically connected to the conductor exposed in the contact hole.

The contact hole for embedding the thin film (electrode wiring) is not limited to one having a width or diameter of 0.6 μm or less, and may have a width or diameter of more than 0.6 μm. Further, the contact hole in which the thin film (electrode wiring) is embedded is not limited to have an aspect ratio of 1 or more, and may have an aspect ratio of less than 1. In addition, various changes can be made within the scope of the matters described in the claims.

[0027]

Example 1 The relationship between the amount of silicon and the cross-sectional state of the aluminum electrode film 11 formed by the above method,
The relationship between the silicon amount and the contact resistance and the relationship between the silicon amount and the surface state of the silicon substrate 1 after the aluminum electrode film 11 was peeled off were examined. The heating temperature of the silicon substrate 1 during sputtering was 370 ° C. The ratio of the amount of silicon to the amount of aluminum in the aluminum electrode film 11 (hereinafter referred to as “Si / Al ratio”) is 0.2%,
It was set to 0.3%, 1.0%, 2.0%, and 6.0% (all are atomic ratios). The Si / Al ratio was changed by changing the thickness of the polysilicon film 15 formed by the CVD method. That is, the Si / Al ratio is approximately equal to the ratio of the amount of silicon supplied to the silicon substrate 1 by the CVD method to the amount of aluminum supplied to the silicon substrate 1 by the sputtering method.

For comparison, an aluminum electrode film 11 having a Si / Al ratio of 0% was also formed. That is, the aluminum electrode film 11 was formed without forming the polysilicon film 15 in advance. The cross-sectional state of the aluminum electrode film 11 and the surface state of the silicon substrate 1 after the aluminum electrode film 11 was peeled off were examined by an electron microscope. Table 1 shows the evaluation results of the cross-sectional state of the aluminum electrode film 11 and the surface state of the silicon substrate 1 after the aluminum electrode film 11 has been peeled off. Si /
Aluminum electrode film 11 having an Al ratio of 0.2 to 6.0%
In each case, voids and the like did not exist inside and the cross-sectional state was good. On the other hand, voids were present in the aluminum electrode film 11 having a Si / Al ratio of 0%.

On the surface of the silicon substrate 1 after peeling the aluminum electrode film 11, the Si / Al ratio is 0.0% and 0.1.
At 2%, traces of aluminum spikes from the aluminum electrode film 11 to the silicon substrate 1 were present. Si
Silicon nodules were present when the / Al ratios were 2.0% and 6.0%. When the Si / Al ratio was 0.3% and 1.0%, the traces of aluminum spikes and the nodules of silicon were not present, which was good.

From the above, the Si / Al ratio is 0.2
It can be seen that% -1.0% is preferable. Si / Al
When the ratio is 0.2%, aluminum spikes are generated, so the Si / Al ratio can be more preferably set to 0.3% to 1.0%. The above is the result when the heating temperature of the silicon substrate 1 is 370 ° C., and when the heating temperature of the silicon substrate 1 is different, the optimum Si / A
It is expected that the l ratio range will be different.

[0031]

[Table 1]

FIG. 3 is a diagram showing the relationship between the Si / Al ratio and the contact resistance. Contact resistance is Si / Al
When the ratio is 0 to 0.3%, it shows an almost constant low value of 0.5 μΩ or less, but when the Si / Al ratio is 1.0% or more, it increases as the Si / Al ratio increases. When the Si / Al ratio is 2.0% or more, the contact resistance is 5.0 to 5.
It becomes about 5 μΩ.

[0033]

Example 2 The relationship between the heating temperature of the silicon substrate 1 when the aluminum electrode film 11 was formed, the cross-sectional state of the aluminum electrode film 11 and the FET On resistance of the obtained semiconductor device was investigated. The Si / Al ratio was 0.3%. The heating temperature of the silicon substrate 1 is 275 ° C., 340 ° C., 410
C, 480, and 550 ° C. Table 2 shows the evaluation results of the cross-sectional state of the aluminum electrode film 11. The aluminum electrode film 11 formed by heating the silicon substrate 1 at a heating temperature of 340 to 480 ° C. did not have any voids and had a good cross-section. On the other hand, silicon substrate 1
The aluminum electrode film 11 formed at the heating temperature of 275 ° C. had voids.

[0034]

[Table 2]

FIG. 4 shows the heating temperature of the silicon substrate 1 and FE.
It is a figure which shows the relationship with T On resistance. The FET On resistance shows a low value of about 80 mΩ when the heating temperature of the silicon substrate 1 is 275 to 410 ° C.
When the heating temperature of 1 is 550 ° C., it becomes as high as about 160 mΩ. From the above, the heating temperature of the silicon substrate 1 is
It turns out that 300-400 degreeC is preferable.

[Brief description of drawings]

FIG. 1 is a MOS manufactured by applying a manufacturing method of the present invention.
It is a schematic sectional drawing which shows the structure of FET.

FIG. 2 is a schematic sectional view for explaining a method for forming an aluminum electrode.

FIG. 3 is a diagram showing the relationship between the contact resistance and the ratio of the amount of silicon to the amount of aluminum in an aluminum electrode.

FIG. 4 is a diagram showing a relationship between a heating temperature of a silicon substrate and a FET On resistance.

[Explanation of symbols]

1 Silicon substrate 4 holes 11 Aluminum electrode film 15 Polysilicon film 16 Aluminum thin film

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4M104 AA01 BB01 BB03 BB40 CC01                       CC05 DD16 DD37 DD78 EE03                       EE16 FF22 FF27 GG09 GG18                       HH05 HH14 HH15                 5F033 HH04 HH09 JJ01 JJ09 KK01                       LL01 MM30 PP06 PP18 QQ09                       QQ37 QQ73 RR04 VV06 WW00                       WW03 XX04 XX09

Claims (5)

[Claims] 1. A method of manufacturing a semiconductor device, comprising forming a thin film containing aluminum so as to fill a contact hole formed on a semiconductor substrate, wherein a thin film containing silicon is formed on an inner surface of the contact hole. A ground film forming step, and an aluminum thin film forming step of forming a thin film containing aluminum so as to fill the contact hole on the surface of the semiconductor substrate while heating the semiconductor substrate after the base film forming step. A method for manufacturing a semiconductor device, comprising: 2. The atomic ratio of the amount of silicon supplied to the semiconductor substrate in the base film forming step to the amount of aluminum supplied to the semiconductor substrate in the aluminum thin film forming step is 0.1% or more and 1 or more. % Or less, The method for manufacturing a semiconductor device according to claim 1, wherein 3. The method of manufacturing a semiconductor device according to claim 1, wherein the base film forming step includes a step of forming a polysilicon thin film by a chemical vapor deposition method. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the aluminum thin film forming step includes a step of forming a thin film containing aluminum by a sputtering method. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the aluminum thin film forming step includes a step of heating the semiconductor substrate to 300 ° C. to 400 ° C.