JPH07193025A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form contact sections having ohmic properties and low resistance onto semiconductor substrates by continuously supplying the inside of a vacuum chamber with the semiconductor substrates. CONSTITUTION:The inside of a vacuum chamber 1, in which a target 2 consisting of titanium is arranged, is supplied with argon gas, a titanium film 5 is deposited on a silicon substrate 3, the inside of the vacuum chamber 1 is fed with argon gas, with which nitrogen is mixed, and a titanium nitride film 6 is deposited on the titanium film 5. The inside of the vacuum chamber 1 is suppled with argon gas again, and nitrogen adhering on the surface of the target 2 is removed while the mixed layer 9 of titanium and nitrogen is deposited on the titanium nitride film 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device in which a highly integrated and low parasitic resistance metal wiring layer is formed on a semiconductor substrate made of silicon.

[0002]

2. Description of the Related Art As semiconductor integrated circuits have become highly integrated, active high-concentration diffusion layers (for example,
In the source / drain region of the MOS transistor or the emitter / base region of the bipolar transistor), the depth of the pn junction portion becomes shallow and the area of the contact interface portion (contact portion) with the metal wiring layer is reduced. In such a semiconductor device, for the purpose of keeping the electrical resistance (contact resistance) at the interface between the active high-concentration diffusion layer and the metal wiring layer ohmic and low, the metal forming the metal wiring layer is formed in the silicon substrate. It is indispensable to provide an intermediate layer (barrier metal) made of a refractory metal or a refractory metal compound between the high-concentration diffusion layer on the silicon substrate and the metal wiring layer for the purpose of preventing diffusion into the metal. Will be. This requirement also exists when forming a contact portion between a silicon substrate and an electrode or a resistor made of polycrystalline silicon.

When an aluminum alloy (Al-Si-Cu alloy) is used as the material of the metal wiring layer, a titanium nitride (TiN) film can be used as the barrier metal. This titanium nitride film has an extremely effective barrier property that can suppress the diffusion of aluminum and copper in the metal wiring layer into the silicon substrate during the heat treatment at 500 ° C. depending on the forming method. This means, for example, the Journal of
Vacuum Science and Technology 21
(1982) pp. 14-18 (J. Vac. Sci. Tech
nol., 21 (1982) pp14-18).

However, since the contact resistance of the barrier metal made of the titanium nitride film is particularly high on the p-type high-concentration diffusion layer, the titanium nitride film and the high-concentration diffusion layer of the silicon substrate are used to reduce the contact resistance. It is essential to provide a titanium (Ti) film between them. This is because the titanium film has a property of reducing the natural oxide film on the silicon substrate, and the titanium film has a lower Schottky barrier height to the p-type silicon substrate than the titanium nitride film. This is described in, for example, Thin Solid Films 96 (1982), pages 327 to 345 (Th
in Solid Films, 96 (1982) pp327-345).

In order to improve productivity, a method of continuously supplying a semiconductor substrate into the vacuum chamber of a sputtering apparatus in which a target is placed in the vacuum chamber and performing sputtering to form a contact portion is known. Although adopted, the interposition of the titanium film between the titanium nitride film and the silicon substrate is effective in reducing the generation of particle dust harmful to the large-scale integrated circuit. The reason is as follows. That is, the particles of titanium nitride attached to the wall of the vacuum chamber are easily separated from the wall, but the particles of titanium are hard to be separated from the wall. Therefore, if titanium particles are generated in addition to the titanium nitride particles in the vacuum chamber, the titanium particles are present, and the titanium nitride particles are also difficult to separate from the wall of the vacuum chamber. For this reason, the film peeling from the wall of the vacuum chamber is reduced, so that the generation of particle dust is reduced.

Further, in a deep submicron MOS type super-large scale integrated circuit, the aspect ratio of the contact hole is large, so that the barrier metal should be deposited to a sufficient film thickness at the bottom of the contact hole by the usual sputter deposition method. Is becoming difficult. Aspect ratio is 0.3
In CMOS of 5 to 0.5 μm, about 2.0,
In a 35 μm DRAM, it will be 4.0 or more, so
The deposited film thickness of the barrier metal on the bottom of the contact hole is often about 5 to 10% of the deposited film thickness on the flat substrate.

In order to solve this problem, a honeycomb-shaped (honeycomb structure) collimator jig is arranged between the target and the substrate in the sputter deposition apparatus to increase the vertically incident component of the sputtered particles deposited on the substrate surface. The method (collimator sputtering method) is used.

By the way, because the collimator jig is arranged between the target and the substrate, and because it is necessary to maintain the uniformity of the in-plane film thickness of the substrate having a large diameter (6 inches or more), It is becoming difficult to dispose a shutter between the target and the substrate as in the conventional case. This can be seen, for example, in Journal of Vacuum Science and Technology A9 (199
1) Pages 261 to 264 (J. Vac. Soc. Tech., A9
(1991) pp261-264).

[0009]

By the way, the inventors of the present invention continuously supply a semiconductor substrate made of silicon into a vacuum chamber not provided with a shutter, and nitride it on the semiconductor substrate through a titanium film. It has been found that when a barrier metal made of a titanium film is formed, a mixed film of titanium and nitrogen is formed instead of the titanium film on the second and subsequent semiconductor substrates. The cause is considered as follows. That is, FIGS. 5A to 5D show a conventional method of manufacturing a semiconductor device. First, FIG.
As shown in, the target 2 made of titanium is placed in the vacuum chamber 1 without a shutter, and the first silicon substrate 3 is loaded into the vacuum chamber 1. Then, when argon gas is supplied into the vacuum chamber 1, argon ions generated from the argon gas collide with the target 2 to release titanium atoms from the target 2 and deposit a titanium film 5 on the silicon substrate 3.

Next, when argon gas mixed with nitrogen is supplied into the vacuum chamber 1 and reactive sputtering is performed, a titanium nitride film 6 is formed on the titanium film 5 as shown in FIG. 5 (b). Is deposited. In this case, the mixed film 7 of titanium and nitrogen adheres to the surface of the target 2.

Next, when the second and subsequent silicon substrates 3 are carried into the vacuum chamber 1 and argon gas is supplied,
As shown in FIG. 5C, a mixed film 8 of titanium and nitrogen is deposited on the silicon substrate 3.

Next, when argon gas mixed with nitrogen is supplied into the vacuum chamber 1 to carry out reactive sputtering, as shown in FIG. 5 (d), the mixed film 8 of titanium and nitrogen is deposited. The titanium nitride film 6 is deposited. in this case,
A mixed film 7 of titanium and nitrogen is again formed on the surface of the target 2.
Adheres. In this way, the second and subsequent silicon substrates 3
Between the titanium nitride film 6 and the titanium nitride film 6, a mixed film 8 of titanium and nitrogen is present instead of the titanium film 5.

As described above, when it is attempted to deposit the titanium nitride film 6 on the silicon substrate 3 through the titanium film 5 by the conventional method, titanium is not deposited on the second and subsequent silicon substrates 3. The mixed film 8 with nitrogen is deposited. Therefore, the second and subsequent silicon substrates 3
The contact resistance to the high-concentration diffusion layer formed above is higher than the resistance value predicted from the Schottky barrier height between the silicon substrate 3 and the titanium film 5 and the impurity concentration of the high-concentration diffusion layer. There's a problem. Therefore, in the semiconductor device obtained by the conventional method,
It becomes difficult to realize a contact portion having ohmic properties and low resistance. This problem is particularly remarkable when a p-type high concentration diffusion layer is formed on a silicon substrate.

In view of the above, according to the present invention, a semiconductor substrate is continuously supplied into a vacuum chamber having no shutter, and the semiconductor substrate and the metal wiring formed on the semiconductor substrate are provided on the semiconductor substrate. It is an object of the present invention to maintain ohmic contact and low resistance when forming a contact portion that electrically connects with a layer.

[0015]

In order to achieve the above-mentioned object, a solution means of the invention of claim 1 is made of silicon in the chamber of a sputtering apparatus in which a target made of metal is arranged in the chamber. A method for manufacturing a semiconductor device, in which a semiconductor substrate is continuously supplied to form a contact portion for electrically connecting the semiconductor substrate and a metal wiring layer formed on the semiconductor substrate on the semiconductor substrate. In the step of forming the contact portion, a sputtering gas made of a first substance is supplied into the chamber, and a metal forming the target is formed on the semiconductor substrate to have a low resistance with respect to the semiconductor substrate. A step of depositing a first metal film, which is a sputtering method, and a sputtering process comprising the first substance and a second substance different from the first substance in the chamber. By supplying ring gas, metal and the second constituting the target on the first metal film
A step of depositing a second metal film made of a compound of the above substance for preventing a reaction between the semiconductor substrate and the metal wiring layer, and supplying a sputtering gas made of the first substance into the chamber, The second substance adhering to the surface of the target is removed, and a third metal film made of a mixture of the metal forming the target and the second substance is deposited on the second metal film. And a process.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the metal constituting the target is a refractory metal.

According to a third aspect of the invention, the refractory metal is titanium and the second substance is nitrogen, in addition to the configuration of the second aspect.

According to a fourth aspect of the present invention, the metal wiring layer is made of a metal containing silicon and the third metal film has a thickness of 8 to 12 nm. It is a thing.

[0019]

According to the structure of claim 1, the semiconductor substrate and the metal wiring layer formed on the semiconductor substrate are formed on the first metal film which is deposited on the semiconductor substrate and has a low resistance to the semiconductor substrate. After depositing the second metal film that prevents the reaction, the second substance that is generated when depositing the second metal film and is attached to the surface of the target is removed, and the second metal film is deposited on the second metal film. Since a step of depositing a third metal film made of a mixture of the metal forming the target and the second substance is provided, when depositing the first metal film on the second and subsequent semiconductor substrates, The second substance attached to the surface of the target has been removed. Therefore, the first metal film, which is not mixed with other substances and has a low resistance with respect to the semiconductor substrates, is deposited on the second and subsequent semiconductor substrates.

According to the second aspect of the present invention, since the metal constituting the target is a high melting point metal, the ohmic resistance and the low resistance which are particularly required when the high melting point metal is deposited on the semiconductor substrate made of silicon. It is possible to realize various contact parts.

According to the structure of claim 3, since the refractory metal is titanium and the second substance is nitrogen, there is a problem when a titanium nitride film is deposited on a semiconductor substrate made of silicon via a nitride film. It is possible to reliably secure the ohmic property and the low resistance of the contact portion.

According to the structure of claim 4, since the thickness of the third metal film is 8 nm or more, the nitrogen adhering to the surface of the target is surely removed. Further, since the thickness of the third metal film is 12 nm or less, even if the silicon contained in the metal wiring layer reacts with the titanium forming the third metal film, the silicon in the metal wiring layer is substantially removed. Never decreases.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings.

1 (a) to 1 (c), a target 2 made of titanium is placed in a vacuum chamber 1 without a shutter, and a silicon substrate 3 is continuously carried into the vacuum chamber 1 to obtain a silicon substrate 3. 3 shows a step of forming a contact portion for electrically connecting the metal wiring layer formed on the silicon substrate 3 and the metal wiring layer.

First, when argon gas is supplied into the vacuum chamber 1, argon ions generated from the argon gas collide with the target 2 as shown in FIG.
Titanium atoms are released from the target 2 and the titanium film 5 is deposited on the silicon substrate 3.

Next, when argon gas mixed with nitrogen is supplied into the vacuum chamber 1 and reactive sputtering is performed, a titanium nitride film 6 is formed on the titanium film 5 as shown in FIG. 1 (b). Is deposited. In this case, the mixed film 7 of titanium and nitrogen adheres to the surface of the target 2.

Next, when argon gas is supplied again into the vacuum chamber 1, as shown in FIG. 1C, the mixed film 7 of titanium and nitrogen adhering to the surface of the target 2 is desorbed from the target 2, An extremely thin mixed film 9 of titanium and nitrogen is deposited on the titanium nitride film 6. A suitable film thickness of the mixed film 9 of titanium and nitrogen is 8 to 12 nm. The reason is that when the thickness of the mixed film 9 of titanium and nitrogen is thinner than 8 nm, the mixed film 7 of titanium and nitrogen adhered to the surface of the target 2 is not sufficiently removed,
On the other hand, when the film thickness of the mixed film 9 of titanium and nitrogen is thicker than 12 nm, the leakage current increases if the metal wiring layer containing silicon is formed on the contact portion. For example, when a metal wiring layer made of an aluminum alloy (Al-1.0% Si-0.5% Cu) is formed on the mixed film 9 of titanium and nitrogen, aluminum and Silicon reacts with titanium constituting the mixed film 9 of titanium and nitrogen to form a Ti—Si—Al based compound, and silicon in the metal wiring layer is reduced. Therefore, silicon in the silicon substrate 3 diffuses to the metal wiring layer side or alloys with aluminum of the metal wiring layer, which causes an increase in junction leakage current. However, when the film thickness of the third metal film is 12 nm or less, the silicon in the metal wiring layer does not substantially decrease, so that the junction leakage current does not increase.

Through the above steps, the formation of the contact portion for electrically connecting the silicon substrate 3 and the metal wiring layer formed on the silicon substrate 3 is completed. And 2
When the first and subsequent silicon substrates 3 are carried into the vacuum chamber 1 and argon gas is supplied into the vacuum chamber 1, the titanium-nitrogen mixed film 7 adhering to the surface of the target 2 has already been removed. Therefore, as shown in FIG. 1A, titanium atoms are emitted from the target 2 and a titanium film 5 containing no nitrogen is deposited on the silicon substrate 3.

FIG. 2 shows a sectional structure of a contact portion of an ultra-large scale integrated circuit device of the deep submicron level formed by the above method. Hereinafter, a method of forming the contact portion of the ultra large scale integrated circuit device will be described with reference to FIG.

An n-type high-concentration diffusion layer is formed by ion-implanting arsenic (As) on the surface of the silicon substrate 3 having a plane orientation (100) or boron fluoride (BF).
₂ ) is ion-implanted into the n-type well region to form the p-type high concentration diffusion layer. Next, CV
After the interlayer insulating film 4 made of a silicon oxide film is deposited on the silicon substrate 3 by the D method, heat treatment at 850 to 900 ° C. is performed to activate the implanted impurity ions. Next, after a contact hole penetrating to the surface of the silicon substrate 3 is opened in the interlayer insulating film 4 by a dry etching method, cleaning by a wet method and removal of the silicon natural oxide film are performed. Next, the titanium film 5, the titanium nitride film 6, and the mixed film 9 of titanium and nitrogen are sequentially deposited on the interlayer insulating film 4 and the silicon substrate 3 exposed in the contact hole by the method described above. In this case, a high-purity titanium film 5 is deposited on the silicon substrate 3. Next, a blanket tungsten CVD method is used to deposit a tungsten film on the entire surface of the mixed film 9 of titanium and nitrogen, and then an etchback method is performed on the tungsten film to form the tungsten film in the contact holes. The plug 10 is formed. Next, a metal wiring layer 11 made of an aluminum alloy is formed on the mixed film 9 of titanium and nitrogen and the plug 10 by a sputter deposition method. Next, a resist pattern is formed on the metal wiring layer 11 by an ordinary photolithography technique, and the metal wiring layer 11, the mixed film 9 of titanium and nitrogen, the titanium nitride film 6, and the titanium film are formed using the resist pattern as a mask. The laminated film of 5 is dry-etched to form a laminated metal wiring layer. After that, heat treatment is performed at a temperature of 450 ° C. in a mixed forming gas of hydrogen and nitrogen to complete an ohmic contact portion having low resistance.

FIG. 3 shows the relationship between the contact hole diameter and the contact resistance as a characteristic of a fine ohmic contact portion having a high aspect ratio formed by the above-mentioned method. The contact with the p-type high concentration diffusion layer is shown in FIG. The case where the part is formed by the conventional method and the case where the part is formed by the method of the present invention are shown. As is apparent from FIG. 3, according to the method of the present invention, low resistance is ensured even in a fine contact portion having a contact hole diameter of 0.4 μm.

FIG. 4 shows p− of the contact portion as a characteristic of the ohmic contact portion formed by the above method.
It is a histogram showing the distribution of the junction leakage current of the n-junction, where (a) is the case where it is formed by the conventional method,
(B) is a case where it is formed by the method of the present invention. Further, FIG. 4 shows the junction leakage current of the pn junction between the n ⁺ -type high concentration diffusion layer formed in the p-type well region and the p-type well region. As the measurement conditions, a reverse bias of 5.0 V was applied and the junction area was 320,000 μm ^2.
The contact area is 4,357 μm ² and the film thickness of the mixed film 9 of titanium and nitrogen is 10 nm. Figure 4
As is clear from the graph, the contact leakage current distributions of the contact formed by the conventional method and the contact formed by the method of the present invention are almost equal. As described above, when the metal wiring layer 11 made of an aluminum alloy is formed on the mixed film 9 of titanium and nitrogen, the mixed film 9 of titanium and nitrogen and aluminum and silicon which form the metal wiring layer 11 is formed. There is a risk that the titanium constituting the titanium reacts with each other to increase the junction leakage current. However, in this embodiment, the junction leakage current did not increase. Therefore, titanium and nitrogen are not formed on the titanium nitride film 6. It can be judged that the amount of silicon in the metal wiring layer 11 was not substantially reduced despite the formation of the mixed film 9.

As described above, according to this embodiment, the titanium film 5 and the titanium nitride film are formed on the silicon substrate 3 by using the sputter deposition apparatus (for example, collimator sputter deposition apparatus) in which the shutter is not provided in the vacuum chamber 1. Membrane 6
In continuously depositing, a mixed film 9 of titanium and nitrogen having a film thickness of about 10 nm is deposited on the titanium nitride film 6, and the contact portion is mixed with the titanium film 5, the titanium nitride film 6 and the titanium and nitrogen. By having a three-layer structure composed of the film 9,
Since it is possible to avoid the situation where nitrogen is mixed into the lowermost titanium film 5, it is possible to form an ohmic contact portion having low resistance on the silicon substrate 3.

In the present embodiment, the contact portion has a three-layer structure including the titanium film 5, the titanium nitride film 6 and the mixed film 9 of titanium and nitrogen, but instead of this, [Table 1 ], It is possible to employ a combination indicated by a circle. For example, boron (B) and titanium (Ti)
In the case of the combination of the above, a three-layer structure of a titanium film, titanium boride and a mixed film of titanium and boron is formed.

[0035]

[Table 1]

[0036]

According to the method of manufacturing the semiconductor device of the first aspect of the present invention, the reaction between the semiconductor substrate and the metal wiring layer is prevented on the first metal film having a low resistance with respect to the semiconductor substrate. After depositing the second metal film, the second substance adhering to the surface of the target when depositing the second metal film is removed, and the metal constituting the target on the second metal film and the metal Since a step of depositing a third metal film made of a mixture with the second substance is provided, when depositing the first metal film on the second and subsequent semiconductor substrates, the first metal film deposited on the surface of the target is deposited. Since the second substance has been removed, the second substance is not mixed in the first metal film deposited on the second and subsequent semiconductor substrates. Therefore, it is possible to reliably manufacture the semiconductor device in which the ohmic and low-resistance contact portion is formed on the semiconductor substrate.

According to the method of manufacturing a semiconductor device of the second aspect of the present invention, since the metal constituting the target is a refractory metal, it is particularly desired when the refractory metal is deposited on the semiconductor substrate made of silicon. It is possible to surely realize a contact portion having ohmic resistance and low resistance.

According to the semiconductor device manufacturing method of the third aspect of the present invention, since the refractory metal is titanium and the second substance is nitrogen, titanium nitride is formed on the semiconductor substrate made of silicon via the nitride film. The ohmic property and low resistance of the contact portion, which are problems when depositing the film, are surely secured.

According to the semiconductor device manufacturing method of the fourth aspect of the present invention, since the thickness of the third metal film is 8 to 12 nm, the nitrogen adhering to the surface of the target can be reliably removed and the metal film can be removed. Even if the silicon contained in the wiring layer reacts with the titanium forming the third metal film, the silicon in the metal wiring layer does not substantially decrease, so that the silicon of the semiconductor substrate becomes the metal wiring layer. It is possible to avoid a situation where the junction leakage current increases due to diffusion or alloying with the metal forming the metal wiring layer.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing each step of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a contact portion of an ultra-large scale integrated circuit device formed by a method of manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a contact hole diameter and a contact resistance in a contact portion formed by a method for manufacturing a semiconductor device according to an embodiment of the present invention.

4A and 4B show a relationship between a junction leakage current and a frequency of occurrence in a contact portion of a semiconductor device, FIG. 4A shows a case of a contact portion obtained by a conventional method, and FIG. 4B shows a relation by a method of the present invention. This is the case of the contact part.

FIG. 5 is a cross-sectional view showing each step of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

1 vacuum chamber 2 target 3 silicon substrate (semiconductor substrate) 4 interlayer insulating film 5 titanium film (first metal film) 6 titanium nitride film (second metal film) 7 mixture of titanium and nitrogen adhering to the target surface Film 8 Mixed film of titanium and nitrogen deposited on silicon substrate 9 Mixed film of titanium and nitrogen deposited on titanium nitride film (third metal film) 10 Plug made of tungsten film 11 Metal wiring layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/3205 21/768 29/40 Z 8826-4M

Claims (4)

[Claims] 1. A semiconductor substrate made of silicon is continuously supplied into the chamber of a sputtering apparatus in which a target made of metal is placed in the chamber, and the semiconductor substrate, the semiconductor substrate and the semiconductor substrate are provided on the semiconductor substrate. A method of manufacturing a semiconductor device, comprising forming a contact portion for electrically connecting to a metal wiring layer formed in the step of forming the contact portion, wherein the step of forming the contact portion includes forming a sputtering gas containing a first substance in the chamber. Supplying and depositing on the semiconductor substrate a first metal film made of a metal forming the target and having a low resistance with respect to the semiconductor substrate; and a step of depositing the first substance in the chamber. A sputtering gas composed of a second substance different from the first substance is supplied, and a metal constituting the target is formed on the first metal film. Depositing a second metal film made of a compound of the second substance and preventing a reaction between the semiconductor substrate and the metal wiring layer; and supplying a sputtering gas made of the first substance into the chamber. And removing the second substance adhering to the surface of the target, and on the second metal film, a third metal film made of a mixture of the metal forming the target and the second substance. And a step of depositing the semiconductor. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the metal forming the target is a refractory metal. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the refractory metal is titanium and the second substance is nitrogen. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the metal wiring layer is made of a metal containing silicon, and the thickness of the third metal film is 8 to 12 nm.