JPH0461322A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the reliability of the contact of a semiconductor device by nitriding the first titanium film formed on the bottom of a contact hole and containing a little amount of oxygen and coating the first film in the contact hole with the second film of a wiring metal. CONSTITUTION:An SiO2 film 3 having a thickness of 0.8-1.0mum is formed on an Si substrate by a CVD method and a contact hole having a width of 0.5-0.7mum is formed through the film 3. By performing ion implantation from the bottom of the hole 4, a diffusion layer of 4X10<15>cm<-3> in arsenic concentration and 2X10<15>cm<-3> in boron concentration is formed. Sputtering is performed under a condition of Ar-0.01vol.% O2 and 0.5mTorr in pressure by using a pure titanium target having a five-nine purity and a Ti-Otrace (titanium containing very little oxygen) is formed on the entire surface of the Si substrate l to a thickness of 200-400Angstrom . Thereafter, the Si substrate is subject to high-speed lamp annealing for 30 seconds at 500 deg.C so as to make nitrogen to get into the entire body of the Ti-Otrace film 5. Finally an Al-1% Si film is vapor- deposited to a thickness of 0.7mum so as to form a wiring layer.

Description

[Detailed Description of the Invention] [Summary] A method for manufacturing a semiconductor device that includes a step of depositing a multilayer structure of barrier metal and interconnection material in a contact hole of a semiconductor substrate, the present invention relates to a method for manufacturing a semiconductor device that includes a step of depositing a multilayer structure of barrier metal and wiring material in a contact hole of a semiconductor substrate, and the reliability of the contact is improved by using a barrier metal deposition method with less dust. The purpose of the present invention is to provide a method of forming an insulating film on a semiconductor substrate, forming a contact hole in the insulating film, and forming titanium, molybdenum, or tungsten mixed with a trace amount of oxygen at the bottom of the contact hole. a step of heating the first film in an ammonia or nitrogen plasma atmosphere to nitride it; and a step of depositing a wiring metal as a second film in the contact hole. Configure it as follows.

[Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and more specifically, a semiconductor device having a step of depositing a multilayer structure of metal-nitride barrier-wiring material in a contact hole of a semiconductor substrate. Relating to a manufacturing method.

[Prior Art] In recent years, the following problems have arisen due to the reduction in contact hole size accompanying miniaturization of devices.

■Increase in contact resistance By using Al containing St about 1% as the wiring material,
In the process of contacting the wiring with the N-type diffusion layer of the Si substrate through a contact hole with an aspect ratio (ratio of height to diameter of the contact hole) of 1 or less and a diameter of approximately 0.8 μm or less, after forming the A1 wiring. 45 in process
Since heat of about 0° C. is applied to the Al-Si interface, the Si of the substrate may be epitaxially oriented with respect to A1 in such a high temperature state, and the interface may become conductive. As a result, the proportion of the semiconductor-conductor contact portion at the interface has decreased, leading to an increase in contact resistance.

■Decrease in the deposition rate of aluminum When depositing aluminum (in the following explanation, pure aluminum and aluminum alloys are collectively referred to as "aluminum") by sputtering, all the aluminum particles flying toward the substrate are It has a directionality. That is, the aluminum film does not grow gradually from the bottom of the contact hole, but grows simultaneously on the bottom and side surfaces. When depositing into a contact hole with an aspect ratio of about 0.6, the problem of reduced coverage does not occur, and the contact hole is completely filled with aluminum. However, when the aspect ratio becomes approximately 1 as the diameter of the contact hole decreases, the particles of the aluminum particles adhering to the side surfaces of the contact hole 4 (see Figure 4) grow into an eaves 7 shape, and the particles move downward. So-called shadowing occurs, which impedes access and results in insufficient filling of the contact hole with aluminum.

As a countermeasure for (1) and (2), it has been proposed to use a double film of titanium nitride (barrier metal) and aluminum.

Titanium nitride is effective as a countermeasure to prevent the reaction between A1 and Si, and titanium nitride has a strong tendency for sputtered particles to fly in one direction and grow perpendicular to the substrate surface. This is effective as a countermeasure against ■.

T i W (titanium tungsten) and W (
tungsten). However, from the viewpoint of the reaction temperature between AI and barrier metal, titanium nitride is more stable than TiW and W at higher temperatures, so the film thickness of the barrier metal can be made thinner.
There is an advantage that the aluminum used as the distribution line can be made thicker. Therefore, it is very beneficial to use titanium nitride as a barrier metal in contact holes where aluminum coverage is poor and disconnection is likely to occur, in order to improve the reliability of the contact. The reliability of the contact here refers to the ability to prevent performance deterioration due to a gradual increase in resistance when a reliability test is performed at 150 to 200°C, even though the device operates, and the ability to prevent performance deterioration due to a gradual increase in resistance when the device operates, but when a reliability test is performed at 150 to 200°C. This refers to preventing the increase in electrical conductivity.

Titanium nitride is formed by sputtering a high-purity Ti (about 5 nines) target in an argon/nitrogen atmosphere;
Two methods are used to form the film: one is to sputter a titanium nitride target in an argon atmosphere.

Since titanium nitride is a hard and brittle material, it is likely to crumble into dust when a titanium nitride target comes into contact with or lightly collides with stainless steel, which is a typical constituent material of sputtering equipment. Stainless steel is also prone to wear when rubbed by a titanium nitride target (and dust is likely to be generated from the worn parts. These dust adheres to the chamber and is taken into the substrate during sputtering, contaminating the device. However, nitride Since the titanium target can be used as is in the sputtering equipment for aluminum wiring, there is an advantage in that a dedicated titanium nitride sputtering equipment is not required.

High-purity titanium is obtained with extremely high purity.
Contact resistance becomes stable. In addition, high-purity titanium has almost the same hardness as stainless steel, etc., and has excellent ductility, so it generates less dust. Furthermore, in the sputtering method using a titanium target, dust can be further reduced by first bombarding the entire sputtering apparatus with Ar to remove dust, then switching to an Ar+N atmosphere and depositing TiN.

Therefore, a method using high-purity titanium as a target is superior.

[Problems to be Solved by the Invention] Contact resistance increases when titanium nitride is brought into direct contact with the diffusion layer of the Si substrate.
It is necessary to dope the diffusion layer with s, B, etc. However, titanium (T f ) between the titanium nitride and the Si substrate
The impurity concentration of the diffusion layer is 4X 10"am-
The concentration can be as low as 3 (As), 2 x 10"cm-" (B), which is the usual low concentration, and defects in the diffusion layer due to high concentration can be avoided.

Since the growth direction of Ti in sputtering is more similar to that of aluminum than that of titanium nitride, there is a concern that the deposition rate may decrease, but this problem does not occur by reducing the film thickness to 200 Å or less. Note that the film thickness referred to here is the thickness of the Ti film deposited on the surface of the substrate, and within the contact hole, a film thickness of Ti that is a fraction of that film thickness is deposited.
The exact film thickness is expected to have a margin of error of over 10 people due to measurement errors.

By forming the multilayer structure of Si (substrate) -Tf-TiN-AI as described above and making the Ti film thinner, the above
, ■ All problems of dust generation and high concentration of the diffusion layer of the substrate can be solved. However, it has been found that reducing the Ti film thickness to about 200 layers causes the problem that contact between the source and drain of the P-channel Mo3 cannot be established. Although the details of the cause are unknown,
In O8 between the P channels, a reaction between the impurity B and Ti to form TiB is likely to occur (this is likely to occur, and the difference in work function between Ti and B-containing Si increases. When the Ti film thickness increases) Although there is no increase in the contact resistance (■) of the source/drain, etc., when we experimentally determined the current curve for N-channel MoS gate voltage changes, we found that break through is likely to occur at low voltages.This problem The Ti film thickness that does not cause this is 200~
400 people (expected film thickness inside the contact hole is 50-70
person). However, it is difficult to control the Ti film thickness within such a narrow range in the manufacturing process of commercial products. Therefore, it is an object of the present invention to provide a method for increasing the reliability of contacts in contact holes using barrier metal deposition means that generates less dust.

[Means for Solving the Problems] In order to achieve this object, the method for manufacturing a semiconductor device of the present invention includes a step of forming an insulating film on a semiconductor substrate, a step of forming a contact hole in the insulating film, and a step of forming a contact hole in the insulating film. a step of depositing a first film of titanium, molybdenum, or tungsten mixed with a trace amount of oxygen at the bottom of the contact hole; a step of heating the first film in an ammonia or nitrogen plasma atmosphere to nitride it; and a step of nitriding the first film in an ammonia or nitrogen plasma atmosphere; The method is characterized by comprising a step of depositing a barrier metal as a second film on the first film, and a step of depositing a wiring metal on the second film.

Hereinafter, the structure of the present invention will be explained mainly using a specific example of titanium.

In the present invention, in order to reduce the generation of dust, titanium nitride is not deposited from the beginning, but titanium containing a trace amount of oxygen (hereinafter referred to as Ti-0t) is first deposited.

(denoted as ac.) is applied. If the oxygen content in the T 10 trace is too high, for example 1%, nitriding becomes impossible. Further, even if oxygen is mixed to such an extent that titanium oxide is detected by X-ray diffraction or the like, nitriding becomes impossible, and the resistivity becomes high, deteriorating the performance as a parimetal. Furthermore, a normal titanium target has a purity of about 5 nines and contains about 250 ppm of oxygen, and when this is sputtered, a considerable portion of the oxygen in the target is thought to be incorporated into the titanium film. At an oxygen concentration of , silicide due to the reaction between Ti and Si cannot be avoided. Since this reaction rate is affected by impurities in Si, in CMoS, the thickness of the TiN film formed after nitridation differs for each Mo3 element.

In the present invention, the trace oxygen of T L Otrace is a value between the above upper and lower limits. T f -Otrac
Even if the film thickness of e is varied over a wide range of 200 to 600, it does not affect the characteristics of the device.

The deposition of Ti and Otrace is followed by its nitriding. The thermal nitriding method adopted for this nitriding is a method that generates less dust. Nitriding is carried out with ammonia or plasma nitrogen. Nitrogen (N2) can also nitride Ti, but
Because the reaction temperature with Ti is high (800°C or higher),
Reactions between Ti and Si are also likely to occur (this is undesirable. Since Tf 0tr1e is difficult to react with Si, almost all of the Ti in Ti-0trac- is converted to titanium nitride. Here, what is titanium nitride? This refers to a substance detected as TiN in an X-ray diffraction spectrum, etc. However, in the thickness direction of titanium nitride, the nitrogen concentration is lower on the substrate side, so even if the entire barrier metal is detected as TiN, it is not stoichiometric. It contains titanium nitride and titanium nitride with a specific stoichiometric composition.Although oxygen remains in titanium nitride and is detected in qualitative analysis, it is not detected in the spectrum of Ti0N.Such TiN is As a metal, it exhibits excellent performance similar to that of TiN manufactured using a normal manufacturing method.

As the ammonia atmosphere for nitriding, 100% NH or Ar NHz mixed gas can be used, and the nitriding temperature is preferably ~600°C.

When nitriding ammonia in a nitrogen plasma excited under reduced pressure by high frequency (microwaves of about 13,56 MHz), Ti-O is removed at a very low temperature of 300 to 400°C.
By nitriding the trace, its reaction with Si can be extremely reduced. Furthermore, Mo has lower stability at high temperatures than Ti, W, etc., and there is a concern that high-temperature nitriding may cause defects in the film, but plasma nitriding does not have such problems.

Ti with a purity of 5 nines or more in the first film deposition process
By using a target of , W or Mo, a film of Ti or the like can be stably deposited. If the purity of the target is lower than this (then it will be difficult to deposit the film,
The target is mixed with oxygen in advance (possibly T
It is not possible to create x tcm. T during sputtering
To make f Ozrac*, the oxygen is preferably 0.
The first film is deposited by sputtering in an argon atmosphere containing 0.05 to 0.1% by volume.

Additionally, T i Otrace can be created by ion implantation. In this case, in the first film deposition process, sputtering is performed in an argon atmosphere using a Ti, W, or Mo target with a purity of 5 nines or more, and then oxygen is ion-implanted to form the first film. Deposit the membrane. The amount of oxygen ion implanted is 1 to 5 X I O"/cm"
It is preferable that it is in the range of .

Subsequently, the wiring material is deposited in a conventional manner. Although the wiring material is not particularly limited, the method of the present invention is suitable for Al-Si type wiring materials.

[Function] Conventionally, it is known to nitride Ti to form a barrier metal, and it is also known to oxygenate Ti, but in the invention as claimed in claim 1, T l -Ot
By first forming a race and first nitriding it, the Ti-Otrace is prevented from being turned into silicide due to the trace amount of oxygen contained in the Ti-Otrace at high temperature during nitriding, and is turned into TiN in the next step. Normal Ti is 55
At around 0°C, it is unavoidable that the interface with the Si substrate becomes silicided and at the same time the Si on the substrate surface is consumed. Therefore, simply nitriding Ti using the conventional method will lead to poor contact, but it is possible to prevent oxygen from flowing from the surface to the interface. Contained T 1
Nitriding the 0 trace prevents reaction with the Si of the substrate; the T L Otrace easily reacts with nitriding media and converts to TiN, providing good contact.

Although different from the method of the present invention, oxygen was included (oxy
As a method of forming TiN (generated),
TiN is produced by heating i in an NH atmosphere, and then 0
A method of heating in two atmospheres is known. However, in this method oxygen does not help prevent silicide formation during nitridation.

Since the nitriding using ammonia and plasma nitrogen employed in the method of claim 1 can nitride the entire thick T f Otrmc*, it is possible to form a thick barrier metal layer, and the performance of the barrier metal (for example, wiring and (prevention of reaction with the substrate) is enhanced. Plasma nitriding according to the second aspect has the advantage of being a low-temperature process, so it is highly effective when it is desired to minimize undesired reactions of various materials as devices become smaller.

The T L -Otrace formation described in claims 3 and 4 is a highly reliable method in terms of adhesive properties, amount of impurities, electrical properties, etc. of the first film, and is also effective in controlling the mixing of a trace amount of oxygen. This is an excellent method. Further, since the method according to claim 4 is carried out in an inert atmosphere, it is an effective method for converting Mo, which becomes extremely unstable when oxidized, into MOOtrace.

Al-Si was selected in consideration of stability when the wiring is exposed to high temperatures in the process after wiring formation.

It is currently the mainstream wiring material. Al according to claim 5
-Si is suitable as a wiring material to which a method of nitriding a T 1 01 rac* film in an ammonia atmosphere is applied. In other words, Al-Si has excellent heat resistance;
The Si atoms in the Ti-0trac have a higher chemical affinity with A1 than with Ti-0trac, and the Ti-0tr@e* crystal is relatively equiaxed, and even after nitriding, there is little development of columnar crystals, so it is a columnar crystal. There are grain boundaries that extend straight towards the Si substrate as shown in (
, the atoms constituting the wiring move toward the Si substrate by passing through the grain boundaries in the shortest distance, so that no reaction with the Si substrate occurs. Therefore, contact failure is unlikely to occur at high temperatures during the nitriding process.

On the other hand, in the future, in consideration of electromigration, there is a tendency for wiring to be replaced with one that does not contain Si but contains Cu or Ti instead. However, in this case, measures must be taken to prevent such undesirable phenomena. (2) Since Al-Cu/Ti has higher reactivity with TiN than Al-Si, there is a risk that aluminum may penetrate the thermally nitrided TiN film. ■TiN easily forms columnar crystals, and A1 and Si can pass through the straight grain boundaries.
will mutually diffuse over the shortest distance. ■Al-Ti/Cu
Since the solid solubility of Si in the alloy (wiring) is very high, the diffusion of (1) tends to proceed, which tends to cause defects such as lattice defects at the Si substrate interface. In order to avoid these ■, ■, ■, we tried to form a thick TiN film, and the reaction temperature was 550℃.
When the temperature exceeds .degree. C., the reaction between Ti and Si tends to occur preferentially over the reaction between NH and Ti.

Considering such problems at high temperatures, AI-T i /
It is considered that low-temperature plasma nitriding according to claim 2 is effective for Cu-flanked wiring materials.

The present invention will be explained in more detail with reference to Examples below.

[Example] A CVD Te SiOz film 3 with a thickness of 0.8 to 1.0 μm was formed on the Si substrate 1 shown in FIG.
．． A contact hole 4 of 5 to 0.7 μm is opened. Ion implantation is performed through contact hole 4, and the As concentration is 4.
X 1018cm-”, B concentration is 2×10”crn
-" diffusion layer 2 is formed.

Using a commercially available pure titanium target with a purity of 5 nines,
Ar-0.01% by volume O6 atmosphere (pressure 5.0mTor
ri-Otrace film 5 (first
) is applied to the entire surface of the Si substrate 1 to a thickness of 200 to 400 layers.

Subsequently, the Si substrate 1 is subjected to high-speed lamp annealing at 500° C. for 30 seconds in an NH3 atmosphere (commercially available pure ammonia is used, pressure is 1 atm or more) to infiltrate the entire Ti-Otrae@ film 5 with nitrogen.

Note that Ti sputtering may be performed in an Ar atmosphere instead of the Ar-0□ atmosphere, and oxygen ions may be implanted at a dose of 10 lffCm-2.

Following the process shown in Figure 3, At-1%Si was deposited to a thickness of 0.7 μm.
to form a wiring layer.

[Effects of the Invention] As explained above, according to the present invention, a film excellent as a barrier metal can be deposited by a method that reduces dust.

[Brief explanation of the drawing]

FIG. 1 shows an oxygen-containing titanium film (Ti-Otr) according to the present invention.
ae*) A diagram showing the deposition process, Figure 2 shows the contact hole opening process, Figure 3 shows the nitriding process, and Figure 4 shows the wiring layer formation process when the aluminum deposition rate is poor. FIG. 1-8i substrate, 2-diffusion layer, 3-SiOz film, 4-contact hole, 5 TI 0trac* film
8 傳Ti thick eyebrows 1st figure 瑑 1 ↑ ♂ 111 Tatsu super clear 3rd contact HOIL/form HA" 2nd 2M 4': "if:xiiAQa[:,! Figure 4

Claims (1)

[Claims] 1. A step of forming an insulating film on a semiconductor substrate, a step of forming a contact hole in the insulating film, a first layer of titanium, molybdenum, or tungsten mixed with a trace amount of oxygen at the bottom of the contact hole. a step of heating and nitriding the first film in an ammonia or nitrogen plasma atmosphere; and a step of depositing a wiring metal as a second film in the contact hole. A method for manufacturing a semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the nitriding step is carried out at 300 to 400° C. in nitrogen plasma in which ammonia is excited with high frequency. 3. In the step of depositing the first film, sputtering is performed in an argon atmosphere containing less than 0.1% by volume of oxygen using a Ti, W or Mo target with a purity of 5 nines or more to form the first film. 3. The method of manufacturing a semiconductor device according to claim 1, further comprising: depositing. 4. In the step of depositing the first film, sputtering is performed in an argon atmosphere using a target of Ti, W, or Mo with a purity of 5 nines or more, and then the first film is formed by ion-implanting oxygen. 3. The method of manufacturing a semiconductor device according to claim 1, further comprising: depositing. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the wiring material is an Al-Si alloy.