JPH0555166A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a method for manufacturing a semiconductor device, which is capable of easily controlling the film thickness of a contact metal and a barrier metal in a contact electrode and suppressing the generation of particulate projections on the surface of the barrier metal. For the purpose of provision. [Structure] After forming a first titanium film 5 on the surface of a silicon substrate 1, a first rapid thermal annealing (RTA) process is performed in a nitriding atmosphere, and then a second titanium film 8 is further formed. , Second RTA in nitriding atmosphere again
Perform processing.

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. More specifically, the present invention relates to a method for manufacturing a silicon-based semiconductor device having a contact electrode, such as a MOS transistor.

[0002]

2. Description of the Related Art Contact electrodes made of silicon semiconductor are
If an electrode made of a material such as aluminum is directly formed on the silicon in the junction region where impurities are doped, there is a disadvantage that an interaction between the electrode material and the silicon occurs. Therefore, a barrier metal is arranged between the electrode material and the silicon. It is generally practiced to prevent the above mutual reaction.

One of the materials used as a barrier metal is titanium nitride (TiN). Conventionally, TiN used as a barrier metal is formed by a reactive sputtering method or a rapid thermal annealing method (also abbreviated as RTA method).

In the reactive sputtering method, Ti is deposited on silicon.
If N is directly attached, the adhesion is insufficient, and a non-contact portion is likely to be formed between the barrier metal layer and silicon, and sufficient conduction between the electrode and silicon cannot be obtained. After sputtering titanium as a metal thinly, TiN is directly synthesized from titanium and nitrogen by reactive sputtering, and this is deposited on the substrate to form a barrier metal.

In the rapid thermal annealing method, titanium is sputtered on a substrate and then rapid thermal annealing is performed in a nitriding atmosphere to simultaneously form TiN as a barrier metal and titanium disilicide (TiSi ₂ ) as a contact metal. is doing.

[0006]

According to the conventional method,
When the barrier metal of TiN is formed by the reactive sputtering method, fine granular projections are generated on the formed TiN surface. This is because even when nitrogen and titanium are reacted in argon, which is an inert gas, to generate TiN, the flow rate of nitrogen is controlled so that nitrogen and titanium are reacted at a ratio of 1: 1 without fail. This is not always possible, because unreacted titanium adheres to the substrate, and TiN that adheres to the walls in the reaction chamber without being deposited on the substrate later peels off and becomes This is because they adhere.

When the protrusions formed on the surface of the barrier metal are large, they may protrude onto the surface of the electrode formed on the barrier metal, and even if they are not formed, unevenness may occur on the surface of the electrode. As a result, the electrode material is peeled off. As described above, when the barrier metal was formed by the reactive sputtering method and then the electrode was formed, it was not possible to obtain a defect-free electrode with high yield.

On the other hand, when the contact metal TiSi ₂ and the barrier metal TiN are simultaneously formed by the rapid thermal annealing method (RTA method), TiSi
_It was difficult to control the film thickness of each of them because the formation rate of TiN was different from that of TiN, and the former formation rate was faster. That is, as illustrated in FIG. 2, the TiSi ₂ film 24 as an ohmic contact is formed thick (the thickness of the formed TiSi ₂ is 3 times that of the original Ti film).
The TiN film 25 as a barrier metal is thick enough to obtain sufficient barrier properties (generally at least about 1000 Å). Could not reach the required thickness). (In FIG. 2,
21 is silicon of the substrate, and 23 is an insulating film. )

From the above, when the contact metal TiSi ₂ and the barrier metal TiN were simultaneously formed by the RTA method, the reliability of the barrier metal was not sufficient.

The present invention easily controls the film thickness of each of the contact metal TiSi ₂ and the barrier metal TiN in the contact electrode, and suppresses the generation of particulate projections on the surface which can be obtained by the reactive sputtering method. It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of forming a barrier metal.

[0011]

According to the method of manufacturing a semiconductor device of the present invention, a first titanium film is formed on a surface of a silicon substrate, and a first rapid thermal annealing process is performed in a nitriding atmosphere, While nitriding the first titanium film to form the first titanium nitride film, siliconization is performed except for the nitride film having titanium on the surface in the portion in contact with the bonding region,
Next, a second titanium film is formed on the first titanium nitride film, and a second rapid thermal annealing process is performed in a nitriding atmosphere to convert the second titanium film into a second titanium nitride film. Instead, the barrier metal of the contact electrode is formed together with the first titanium nitride film, and at the same time, the previously siliconized titanium under the first titanium nitride film is changed to stable titanium disilicide to make contact. It is a manufacturing method characterized by including a step of forming a contact metal of an electrode.

The method of the present invention will be described with reference to FIG.
As shown in FIG. 1A, in the method of the present invention, first, the first titanium film 5 is formed on the silicon substrate 1. The titanium film can be formed by any convenient method such as sputtering. The silicon substrate 1 is composed of silicon 2, a junction region 3 in which silicon is doped with impurities, and an insulating film 4 having a desired pattern. If the thickness of the first titanium film 5 is too thick, the thickness of the siliconized film formed by the subsequent rapid thermal annealing treatment (hereinafter, simply referred to as “RTA treatment”) increases, so that the thickness of the bonding region 3 increases. Therefore, it should be determined in accordance with the thickness of the junction region of the semiconductor device to be manufactured, since it may cause junction destruction. Generally, the thickness of the finally formed contact metal of titanium disilicide can be about 2.4 to 3 times the thickness of the first titanium film 5. The thickness of the titanium film can be easily adjusted by adjusting the sputtering time when the film is formed by sputtering, for example.

Next, a first RTA process is performed in a nitriding atmosphere such as a nitrogen atmosphere or an ammonia atmosphere to change the first titanium film 5 into a nitride film. At this time,
As shown in (b), the titanium film on the insulating film is entirely nitrided to form the titanium nitride film 6, except that the titanium film in the portion in contact with the bonding region has a thin nitride film 6 on the surface. Thus, the titanium 7 siliconized by the silicon in the bonding region is formed. This is because the speed of the siliconization reaction is faster than the speed of the nitriding reaction.

The first RTA process should be performed at a temperature sufficient to nitride the titanium film. However, it is not preferable to increase the treatment temperature more than necessary because the diffusion rate of titanium into silicon increases and the thickness of the siliconized titanium 7 increases. Therefore, in general,
The temperature of the first RTA treatment should be up to about 700 ° C, preferably around 700 ° C.
When the RTA treatment is performed at about 700 ° C., the thickness of the siliconized titanium 7 is 2 to 2 times that of the original titanium film 5.
It increases about 2.5 times.

Then, as shown in FIG. 1C, for example, titanium is sputtered on the first titanium nitride film 6,
A second titanium film 8 is formed. The thickness of the second titanium film 8 is substantially the same as the thickness of the titanium nitride film as a barrier metal finally formed on the contact region because the first titanium nitride film 6 on the contact region is considerably thin. To decide. Generally, the thickness of the finally formed titanium nitride film is about 1.3 to 1.4 times the thickness of the second titanium film 8. Therefore, the required thickness of the second titanium film can be determined using this as a guide.

After forming the second titanium film 8, a second RTA is formed.
Perform processing. The second RTA treatment is performed in a nitriding atmosphere in the same manner as the first RTA treatment to remove the second titanium film.
As shown in (d), while changing to the second titanium nitride film 9, it is necessary to change the siliconized titanium formed by the first RTA treatment into stable titanium disilicide. Therefore, the second RTA process is at least about 800
It should be performed at a temperature of ℃, but if the temperature is too high, problems such as diffusion of the doped impurities will occur, so
It is suitable to carry out at about 800 ° C. When the first RTA treatment is performed at around 700 ° C. and the second RTA treatment is performed at around 800 ° C., finally formed Ti is formed.
The film thickness of the contact metal 10 of Si ₂ is the same as that of the first RTA.
The thickness is about 1.2 times the film thickness of the siliconized titanium 7 formed by the processing.

In the silicon substrate on which the contact metal of TiSi ₂ and the barrier metal of TiN are formed in this way, electrodes can be formed by using a metal material such as aluminum according to a usual method.

[0018]

The first RTA treatment performed in the nitriding atmosphere after forming the first titanium film is performed by nitriding the titanium film on the insulating film and the surface region of the titanium film in a portion in contact with the bonding region. While the titanium nitride film is formed, titanium under the surface area of the nitrided portion in contact with the bonding area is siliconized. Since the rate of siliconization of titanium is faster than the rate of formation of titanium nitride, the titanium nitride film on the surface formed in the portion in contact with the bonding region is thin, whereas the titanium under the surface nitride film is Siliconized by the silicon in the junction region to form siliconized titanium that has penetrated into the junction region. The thin nitride film on the surface serves to prevent the second titanium film on the second titanium film from interacting with the silicon in the bonding region in the subsequent second RTA treatment.

In the second RTA treatment which is also performed in the nitriding atmosphere after the second titanium film is formed, all the second titanium film on the first titanium nitride film is changed to the titanium nitride film to form the barrier metal. A titanium nitride film having an effective thickness is formed, and the siliconized titanium formed by the first RTA process is used as stable titanium disilicide to form a contact metal.

[0020]

EXAMPLES Next, the method of the present invention will be further described with reference to examples.

To form a contact metal (TiSi ₂ ) on a silicon substrate having a contact region with a thickness of 3000 Å that is doped with impurities and an insulating film having a desired pattern in which an opening for an electrode to be formed in the contact region is formed. Ti was sputtered. Pressure of Ti sputter is 3mTorr
And the temperature was 200 ° C. in argon, and the flow rate of argon was 100 cc / min. 500 Å Ti under these conditions
A film was formed.

The silicon substrate on which the Ti film was formed was subjected to RTA at about 700 ° C. for about 30 seconds in a nitrogen atmosphere at normal pressure.
Treated, Ti on the insulating film and Ti in contact with the contact region
T which is in contact with the contact region while nitriding the surface of the film
i was siliconized. The thickness of the obtained siliconized titanium was about 1000 to 1200Å, and the lower portion thereof reached the inside of the contact region.

Next, a 1000 Å Ti film was formed on the formed TiN film under the same conditions as above. Then, the substrate is heated at a temperature of about 800 ° C. in a nitrogen atmosphere at atmospheric pressure for about 1 minute
TA treatment was used to nitride the Ti film while converting the previously siliconized titanium in the contact region to stable titanium disilicide (TiSi ₂ ). The thickness of the TiN film as the barrier metal of the contact electrode thus formed is 1300 to 1400Å, and the thickness of the TiSi ₂ film as the contact metal is 1200 to 150.
It was 0Å, and no joint failure was observed. When the surface of the barrier metal was inspected with a dust inspection device, almost no granular projections, which were observed when the barrier metal was formed by the conventional reactive sputtering method, were observed.

An aluminum electrode was formed on the barrier metal thus formed in the usual way. The results of the continuity test between these aluminum electrodes and the bonding area were good.

The operating conditions given here are merely examples, and may be appropriately changed depending on the conditions of the semiconductor device to be manufactured and the conditions of the manufacturing device to be used.

[0026]

As described above, according to the method of manufacturing a semiconductor device of the present invention, the contact metal TiSi ₂
Since the film thickness of is determined by the thickness of the first titanium film and the film thickness of TiN of the barrier metal is determined by the thickness of the second titanium film, both film thicknesses can be easily controlled independently. .. Further, in the method of the present invention, T of the barrier metal is
Since it is not necessary to use the reactive sputtering method in which granular projections are likely to be formed on the iN film surface, the generation of granular projections on the TiN film surface is suppressed as compared with the conventional reactive sputtering method, and a good contact electrode can be obtained. Can be produced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method for manufacturing a semiconductor device of the present invention, in which (a) is a diagram illustrating a step of forming a first titanium film on a silicon substrate, and (b) is a first rapid method. FIG. 6 is a diagram illustrating a thermal annealing treatment step, FIG. 7C is a diagram illustrating a step of forming a second titanium film, and FIG. 6D is a diagram illustrating a second rapid thermal annealing treatment step.

FIG. 2 is a diagram exemplifying a junction breakdown that occurs in a conventional rapid thermal annealing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Silicon substrate 3 ... Bonding area 5 ... First titanium film 6 ... First titanium nitride film 7 ... Siliconized titanium 8 ... Second titanium film 9 ... Second titanium nitride film 10 ... Contact metal

Claims (3)

[Claims] 1. A first titanium film (5) is formed on a surface of a silicon substrate (1), and a first rapid thermal annealing process is performed in a nitriding atmosphere to obtain the first titanium film (5). Is nitrided to form a first titanium nitride film (6), the titanium film at the portion in contact with the bonding region (3) except for the nitride film on the surface is siliconized, and then the first titanium nitride film is formed. (6) A second titanium film (8) is formed on the second titanium film (8), and a second rapid thermal annealing process is performed in a nitriding atmosphere to form the second titanium film (8).
To a second titanium nitride film (9) to form a barrier metal for a contact electrode together with the first titanium nitride film (6), and at the same time, to form the first titanium nitride film (6).
1. A method for manufacturing a semiconductor device, comprising the step of: first converting siliconized titanium (7) into stable titanium disilicide to form a contact metal (10) of a contact electrode. 2. The method of claim 1, wherein the first rapid thermal annealing treatment is performed at a temperature of up to 700 ° C. and the second rapid thermal annealing treatment is performed at a temperature of at least 800 ° C. 3. The method according to claim 1, wherein the nitriding atmosphere is a nitrogen atmosphere or an ammonia atmosphere.