JP2542617B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device with improved wiring layer connection.

(Prior Art) In recent years, as a method of forming an electrode wiring for an opening provided in an insulating film formed on a Si substrate, hydrogen (H ₂ ) and hexafluoride are used instead of a sputtering method of a material containing Al as a main component. A method of forming a W film by a chemical vapor deposition method (CVD method) using a tungsten oxide (WF ₆ ) gas has been proposed. in this way,
Since the reaction rate on the substrate surface is the dominant factor that controls the deposition rate, a significant improvement in step coverage can be realized as compared with the conventional sputtering method and the like.

However, the W film and the underlying oxide film (SiO ₂ film) have weak adhesion, and cannot withstand the stress between the W film and the Si substrate, so that the W film frequently peels. Therefore, the surface shape of the W film loses its flatness and makes subsequent pattern processing difficult. Further, if the W film is thinned so that peeling does not occur, the center part of the opening becomes a recess, so that the insulating film is coated on the upper layer and the second opening is formed immediately above the opening. In this case, the insulating film thickness is locally different. Therefore, it is difficult to perform uniform etching, and there is a possibility that the connection portion may have poor contact.

As a method for solving this problem, recently, a method of providing a metal layer having good adhesion between the W film and the Si substrate has been proposed. In particular, the adhesiveness with the lower layer is good and the electric resistivity itself is 100 μΩcm or less, and the reaction between the W film deposited on the upper layer and the Si substrate located on the lower layer is high temperature (700 ° C or more).
However, nitrides such as Ti, Zr, Hf, Nb, Ta, Mo and W are effective substances that can be blocked.

However, it was found that when the W film was deposited on these metal nitride layers by the CVD method, if the conventional hydrogen reduction method of WF ₆ was used, the growth rate of the W film was extremely slow or the W film was not deposited. . That is, in the CVD method using the hydrogen reduction method of WF ₆ ,
Although a W film having a desired film thickness can be formed on Al, W and Si with good controllability, extremely unstable W film growth was observed on metal nitride, which is the same conductive material. The sputtering method can form a metal film on the metal nitride layer without any problem, but in this case, there is a problem in step coverage as described above. Therefore, there is a demand for a technique for forming a metal film on the metal nitride layer by the CVD method with good reproducibility.

On the other hand, refractory metal nitrides are effective as reaction barriers because they have a large free energy reduction caused by compound formation and conductivity, and are effective as reaction barriers, and tin, ZrN, HfN, etc. have been applied so far. There is. Usually, since the contact resistance between these metal nitrides and Si is high, a silicide is preliminarily interposed between them, or a metal layer is interposed to form a metal silicide by heat treatment. However, if W / TiN / TiSi ₂ / Si structure is realized by using W, which is one of the refractory metals, the outward diffusion of Si atoms becomes remarkable due to the heat treatment exceeding 900 ° C, and the suicide rate of W is extremely high. It gets bigger. In addition, in the Al / TiN / TiSi ₂ / Si structure, TiN
If heat treatment such as slightly oxidizing the surface layer of
Since Al penetrates through TiN and enters the Si substrate at about ℃, the Si layer is liable to cause a junction failure or the like.

(Problems to be Solved by the Invention) As described above, in the conventional method of forming a metal film having a desired thickness on a semiconductor or an insulating film formed thereon or a metal nitride layer formed on a metal film by a CVD method It was difficult to form a metal film having a desired thickness with good reproducibility in a short time. Even if a metal nitride layer is used as a reaction barrier, it is difficult to reliably prevent the reaction between the metal and Si.

The present invention has been made in consideration of the above circumstances, and an object thereof is to enable a metal film to be deposited on a metal nitride layer by a CVD method with good reproducibility and in a short time, thereby improving throughput. An object of the present invention is to provide a method of manufacturing a scaleable semiconductor device.

Another object of the present invention is to provide a method for manufacturing a semiconductor device, which can surely prevent a reaction between metal and Si and can realize a highly reliable metal / Si contact.

[Structure of the Invention] (Means for Solving Problems) The essence of the present invention is to facilitate growth of a metal film on a metal nitride layer by selecting a gas used in the CVD method. . Further, it is to increase the reaction barrier effect by making nitrogen in the metal nitride layer excessive.

That is, the present invention is a method for manufacturing a semiconductor device including a step of forming a metal film via a metal nitride layer on a semiconductor substrate, in which a mixed gas of a metal halogen compound gas and a hydrogen gas containing a silicon-hydrogen compound gas. Is a method of depositing the metal film on the metal nitride layer by a chemical vapor deposition method using.

Further, the present invention provides a method for manufacturing a semiconductor device, which includes a step of forming a metal film on a semiconductor substrate via a metal nitride layer, wherein the metal nitride of the metal nitride layer has an initial average composition of metal-nitrogen. This is a method in which the nitrogen component is formed in excess of the metal nitride containing the largest amount of nitrogen components formed between.

(Operation) According to the present invention, a metal film is formed on a semiconductor substrate by a CVD method with a metal nitride layer interposed therebetween, so that the adhesiveness is good on the semiconductor substrate, and the step coverage and the electrical conductivity are good. It becomes possible to form a wiring layer. Furthermore, in the CVD method for forming a metal film, the inclusion of a silicon-hydrogen compound gas in hydrogen causes a large number of nucleation sites on the metal nitride, which results in a desired film thickness. It is possible to form the metal film in a short time with good reproducibility.

Further, by making the nitrogen of the metal nitride layer excessive,
By precipitating nitrogen in the nitride grain boundary, it is possible to prevent the unreacted metal from remaining in the nitride layer, suppress the diffusion of metal or Si at the grain boundary at the interface with the metal and inside the nitride,
The thermal stability of the / Si structure can be maintained at higher temperatures. Therefore, good contact characteristics and good PN junction characteristics can be obtained. Therefore, the low-resistance wiring can be formed with high reliability, and the density and integration of the semiconductor device can be increased.

(Examples) The details of the present invention will be described below with reference to illustrated examples.

FIG. 1 is a sectional view showing a manufacturing process of a semiconductor device according to a first embodiment method of the present invention. First, FIG. 1 (a)
As shown in, L on a p-type (100) Si substrate 11 with a specific resistance of 6 Ωcm
A 0.8 μm SiO ₂ film 12 is formed by a P-CVD method at 400 ° C. using a mixed gas of SiH ₄ and N ₂ O, and then a 500 Å TiN film (metal nitride layer) 13 is formed. The TiN film 13 was formed by sputtering at a substrate temperature of 200 ° C., a Ti target was set to 5 m Torr in a mixed gas of N ₂ and Ar (50% each).

Next, hydrogen (H ₂ ), monosilane (S
iH ₄ ) and tungsten hexafluoride (WF ₆ ) mixed gas, H ₂ is kept at 0.173 Torr, SiH ₄ is kept at 0.013 Torr, and WF ₆ is kept at 0.065 Torr, and the substrate temperature is 380 ° C. As shown in FIG. 1B, a W film (metal film) 14 having a thickness of 0.2 μm is formed on the TiN film 13. At this time, the deposition time was 2 minutes and 40 seconds. afterwards,
As shown in FIG. 1 (c), the wiring pattern is processed using ordinary lithography and reactive ion etching (RIE).

When performing the above-mentioned CVD method, a cold wall type CVD apparatus as shown in FIG. 2 is used, a plurality of substrates 23 are arranged in a susceptor 22 housed in a reaction furnace 21, and a heater 24 is used.
The substrate was heated by the above method and a predetermined gas was introduced into the reaction furnace 21 to grow a W film, a SiO ₂ film and the like.

Here, the addition amount of SiH ₄ used for growing the W film is 0.
Although it was 013 Torr, the amount of Si contained in the W film at this time was about 1.3 to 1.8% by SIMS analysis. Also, Si
When the growth rate of the W film is plotted against the amount of H ₄ added,
It looks like Figure 3. 0 to 48Å / min without addition of SiH ₄
And 0.013 Torr SiH ₄ partial pressure is 750 Å / min, 0.026 Tor
At r, it was 1400Å / min, and the stability of the growth rate was dramatically improved. Further, when the underlayer was W, the growth rate was stable at 200 Å / min even without the addition of SiH ₄ .

Thus, according to the method of this example, the CV
As a gas used in the D method, SiH ₄ is added to a mixed gas of WF ₆ and H ₂ , that is, H ₂ as a carrier gas is added.
By adding SiH ₄ , the W film 14 can be grown on the TiN film 13 at a sufficiently high speed and with good reproducibility. here,
The TiN film 13 has good adhesion to the underlying SiO ₂ film 12, and the TiN film 13
The adhesion between 13 and the W film 14 is extremely good. Therefore, Si
The W film 14 can be formed on the O ₂ film 12 with good adhesion, which is extremely effective for forming a wiring pattern. Further, there is an advantage that it can be easily realized by simply selecting the type of gas without significantly changing the conventional process.

FIG. 4 is a process sectional view for explaining a second embodiment method of the present invention. This embodiment is an example in which a flattening wiring which doubles as a hole is formed on a base having a deep opening.

First, as shown in FIG. 4 (a), an n ⁺ layer 4 by arsenic (As) doping was formed on the surface of a p-type (100) Si substrate 41 having a specific resistance of 6 Ωcm.
2 is formed, and a SiO ₂ film 43 of about 1.3 μm is formed thereon by the LP-CVD method. Subsequently, an opening 44 having a diameter of 0.5 μm is provided at a desired position on the SiO ₂ film 43 by RIE.

Then, by the LP-CVD method at 650 ° C.
₂ , TiCl ₄ is introduced at a partial pressure of 0.05 Torr, and NH ₃ is introduced at a partial pressure of 0.06 Torr, and a TiN film (metal nitride layer) 45 of about 500 Å is deposited on the entire surface as shown in FIG. 4 (b). . Then, set the substrate temperature to 40
H ₂ at a partial pressure of 0.173 Torr and SiH ₄ at a partial pressure of 0.013 Torr.
WF ₆ was introduced at a partial pressure of 0.065 Torr, and about 300 Å on the TiN film 45.
Then, the W film (metal film) 46 is deposited.

Then, H ₂ with a partial pressure of 0.272 Torr and WF ₆ with a partial pressure of 0.03 Torr are introduced to deposit a W film 47 of about 2000 Å as shown in FIG. 4C. At this time, the W film 47 is formed with good reproducibility without adding SiH ₄ because the underlying film is the W film 46. Then
As shown in FIG. 4 (d), W films 47, 46 and Ti are formed by RIE or the like.
The N film 45 is selectively etched to form a wiring pattern.

As described above, in the method of this embodiment, H ₂ and WF ₆ containing SiH ₃ are first introduced onto TiN, a W film is grown by SiH ₄ reduction, and then W is reduced by H ₂ reduction of only H ₂ and WF _6. The film is growing. Two
Since the growth rate is high in SiH ₄ reduction, the reaction gas concentration is insufficient in the opening with an aspect ratio of 2.6, and the growth rate in the opening is slower than that in the flat portion, so that the step coverage is further enhanced. It is compensated by the excellent H ₂ reduction of. That is, the W film is stably grown on the TiN surface by reduction with SiH ₄ , and then the W film is thickened by reduction with H ₂ . When H ₂ reduction is used directly on TiN, the growth rate is 0 to 48 Å / min depending on the surface condition, but it is stable at 150 Å / min if the W film is formed on TiN. Growth rate is obtained. Therefore, the W films 46 and 47 can be embedded in the opening 44 having a large aspect ratio with good step coverage, which is extremely effective for forming a wiring layer.

FIG. 5 is a process sectional view for explaining a third embodiment method of the present invention. This embodiment is an example in which the selective CVD method is used to fill the conductor film in the opening.

First, as shown in FIG. 5A, an n ⁺ layer 52 is formed by As doping on the surface of a p-type (100) Si substrate 51 having a specific resistance of 6 Ωcm, and a TiN film is deposited on the n ⁺ layer 52 by sputtering. 700 ° C NH ₃
300 Å TiSi ₂ film 53 and 1000 Å TiN heated in the atmosphere
A film (metal nitride layer) 54 is formed. Subsequently, an insulating film 55 having a thickness of 1.3 μm is formed on the TiN film 54. This insulating film 55
Is 0.5 μm of B on a SiO ₂ film formed by 0.8 μm atmospheric pressure CVD method.
It consists of two layers of PSG films. Then, an opening 56 having a diameter of 0.5 μm is formed in the insulating film 55.

Then, at a substrate temperature of 400 ° C., H ₂ with a partial pressure of 0.173 Torr and 0.
By depositing SiH ₄ of 013 Torr and WF ₆ of 0.065 Torr for 5 minutes in a CVD reaction furnace, a W film (metal film) 57 is formed in the opening 56 as shown in FIG. 5B. Selectively formed. At this time, since the W film does not grow on the insulating film in the flat portion and the growth from the bottom, the step coverage does not matter.

FIG. 6 is a process sectional view for explaining the method of the fourth embodiment of the present invention. In this embodiment, in order to reliably prevent the reaction between the metal film and the Si substrate, the metal nitride film between them is made to have excess nitrogen.

First, as shown in FIG. 6 (a), a device isolation oxide film 62 of about 6000Å is formed on a p-type (100) Si substrate 61 having a specific resistance of 4 to 6 Ωcm.
To form. Then, 50 KeV of As is applied to part of the element formation region.
2 × 10 ¹⁵ cm ⁻² ions were implanted at 950 ° C. for 60 minutes to form an n ⁺ type diffusion layer 63. Next, as shown in FIG. 6B, a SiO ₂ film 64 of about 0.3 μm was formed on the entire surface by the LP-CVD method, and a contact hole 64 having a size of about 7,000 to 8,000 Å was opened. Moreover, As is again applied to the contact part at 30 KeV and 1 × 10.
Ion-implant ¹⁵ cm ^-2 , heat treatment at 1000 ℃ for 15 seconds, n ⁺
A layer 63 'was formed.

Next, a 100 Å Ti film is sputter-deposited with argon on the substrate shown in FIG. 6 (b) in a high-vacuum sputtering apparatus, and then in a mixed gas atmosphere of nitrogen and argon (pressure 5 × 10 ^−3). A Ti target is sputtered with Torr) to form a 1000Å TiN _X film (metal nitride layer) 66 on the entire surface as shown in FIG. 6 (c). At this time, x was set to be larger than 1. Next, in a 10% hydrogen + nitrogen mixed gas, 700 ° C,
After changing all 100 Å Ti to TiSi ₂ by heat treatment for 30 minutes,
As shown in FIG. 6 (d), a 0.6 μm Al film (metal film) 67 is deposited on the entire surface. After that, pattern the Al film 67
Sinter at 450 ° C for 30 minutes in 10% hydrogen + nitrogen mixed gas.

In this embodiment, as shown in FIG. 7, the N / Ti of the TiN _X film 66 is
Compared with the case where the ratio is 1 or less (x ≧ 1), the junction leakage current of 0.2 μm can be significantly reduced. 200 × 500 μm ²
When the N / Ti ratio is 0.9 or less with ^respect to the joining area of 10 ^-8 to 10
^-7 A (when voltage 5 V is applied), while N / Ti ratio is 1.1
10- ¹¹ A, at least 1.2 result of inhibited 10- ¹³ A and Al / Si reaction, significant improvement of the junction leakage characteristics were observed.

When W is used instead of Al in the same method, 950 ° C
The silicidation rate of W is 10 Å / min in terms of W thickness when the N / Ti ratio is 1, whereas it is 0.2- when the N / Ti ratio is 1.2.
It decreased to 0.5Å / min, and the reaction barrier effect was significantly improved.

Thus, according to the method of this example, the TiN film 66 interposed between the underlying Si substrate 61 and the Al film 67 to be the wiring layer is made to have excess nitrogen, so that the interface with the Al film 67 and the TiN film 66 are It is possible to suppress the diffusion of Al or Si at the grain boundaries of Al and maintain the thermal stability of the Al / Si structure up to a higher temperature. That is, the reaction barrier effect of the TiN film 66 can be enhanced, and good contact characteristics and good pn junction characteristics can be obtained. Therefore, the low resistance wiring can be formed with high reliability, which is also effective for increasing the density and integration of the semiconductor device.

The present invention is not limited to the method of each of the embodiments described above. For example, in the first to third embodiments, the metal nitride layer is not limited to TiN, but Zr, Hf, Nb, Ta, Mo,
It may be a nitride such as W. As a metal halide gas for forming a metal film, MoF is used instead of WF _6.
It is possible to use ₆ . Further, as the metal film to be arranged between the metal nitride layer and the base substrate, it is possible to use a silicide of another metal or a simple metal such as Al or W instead of TiSi ₂ . In addition to SiH ₄ , hydrogen-silicon compounds are
H ₆ or SiH ₈ may be used. Further, the addition amount of the hydrogen-silicon compound can be appropriately changed according to the specifications.

Further, in the fourth embodiment, the metal film is not limited to Al, W, etc., but may be a metal mainly composed of Cu, Ag, Au, Pt, Pd, Ni, Mo or Cr. Further, the metal of the metal nitride layer is not limited to Ti, and may be any metal mainly composed of Ti, Zr, Hf, Ta or Nb. In addition, various modifications can be made without departing from the scope of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, by using a mixed gas of a metal halogen compound gas and a hydrogen gas containing a silicon-hydrogen compound gas in the CVD method, In addition, a low resistance metal film can be formed with good reproducibility in a short time and with good step coverage. Therefore, the reliability of the wiring layer and the throughput of the semiconductor device can be improved. Further, by forming the metal nitride layer in excess of nitrogen, it is possible to reliably prevent the reaction between the metal film and the underlying substrate, and it is possible to realize a highly reliable metal / Si contact. Is immense.

[Brief description of drawings]

FIG. 1 is a sectional view showing a manufacturing process of a semiconductor device according to a first embodiment method of the present invention, and FIG. 2 is used in the above embodiment.
Schematic diagram showing the CVD device, Fig. 3 shows W by adding SiH ₄
FIG. 4 is a characteristic view showing changes in the film deposition rate, FIG. 4 is a process sectional view for explaining the second embodiment method, FIG. 5 is a process sectional view for explaining the third embodiment method, and FIG. FIG. 7 is a process sectional view for explaining the method of the fourth embodiment, and FIG. 7 is a characteristic diagram showing a change in junction leak current with respect to the N / Ti ratio. 11,41,51 …… Si substrate, 12,43,55 …… SiO ₂ film (insulating film),
13,45,54 …… TiN film (metal nitride layer), 14,46,47,57 ……
W film (metal film), 42,52 …… n ⁺ layer, 44,56 …… Opening part, 53
...... TiSi ₂ film.

Claims (9)

(57) [Claims] 1. A method of manufacturing a semiconductor device including a step of forming a metal film on a semiconductor substrate via a metal nitride layer, wherein a mixed gas of a metal halogen compound gas and a hydrogen gas containing a silicon-hydrogen compound gas is used. A method of manufacturing a semiconductor device, comprising depositing the metal film on the metal nitride layer by a chemical vapor deposition method using. 2. The metal of the metal nitride layer is Ti, Zr, Hf, Nb,
The method for manufacturing a semiconductor device according to claim 1, wherein the method is Ta, Mo or W. 3. The metal halogen compound gas is WF ₆ or M
The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is oF ₆ . 4. The silicon-hydrogen compound gas is SiH ₄ , Si ₂ H ₆
Alternatively, it is Si ₃ H _8;
A method of manufacturing a semiconductor device according to the item. 5. The method of manufacturing a semiconductor device according to claim 1, wherein a diffusion layer, a metal film or an insulating film is formed on the surface of the semiconductor substrate. 6. A method of manufacturing a semiconductor device, comprising the step of forming a metal film on a semiconductor substrate via a metal nitride layer, wherein the metal nitride of the metal nitride layer has an initial average composition of the metal-nitrogen. A method for manufacturing a semiconductor device, characterized in that the nitrogen component is formed so as to be in excess of the metal nitride having the largest nitrogen component formed between the two. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the metal film has a smaller decrease in free energy due to nitriding than the metal of the metal nitride layer. 8. The metal film is made of Al, Cu, Ag, Au, Pt, Pd, Ni, W, M.
7. The method for manufacturing a semiconductor device according to claim 6, wherein the metal is mainly o or Cr. 9. The metal of the metal nitride layer is Ti, Zr, Hf, Ta.
7. A method of manufacturing a semiconductor device according to claim 6, wherein the metal is mainly composed of Nb.