KR970005684B1 - Wiring method in semiconductor manufacturing - Google Patents

Abstract

A method of forming a metal line of a semiconductor device includes the steps of depositing Ti in a contact hole formed on a silicon substrate to form a Ti layer, processing the Ti layer with NH3 plasma, and depositing tungsten nitride on the Ti layer processed with NH3 plasma using chemical vapor deposition method, to form a tungsten nitride layer. Accordingly, the tungsten nitride layer formed using plasma chemical vapor deposition having excellent step coverage is used as a diffusion blocking layer, to minimize the contact resistance.

Description

Method for forming metal wirings for semiconductor devices

1A to 1D are cross-sectional views illustrating an example of a conventional metal wiring forming method.

2A and 2B are graphs for explaining contact characteristics between a conventional tungsten nitride film and a silicon substrate.

3a to 3f are cross-sectional views for explaining an example of a metal wiring forming method according to the present invention,

4 is a graph measuring contact properties with a titanium film, a silicon substrate according to the present invention,

5A and 5B are SEM images comparing the cross sections of the contact openings with and without the NH ₃ plasma treatment.

6a and 6b are graphs comparing the distribution of contact resistance with and without NH ₃ plasma treatment,

7a and 7b are graphs showing the results of the reliability test of the device manufactured according to the present invention,

8 to 11 are cross-sectional views showing embodiments according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming metal wirings of highly integrated semiconductor devices, and more particularly to a method for forming metal wirings using a diffusion barrier.

The degree of integration of semiconductor devices is getting higher, and when design rule is used as aluminum for wirings of 1μm or more, electro-migration phenomenon occurs due to high current density, and silicon (Si) is dissolved into aluminum. Junction spiking occurs, resulting in short impurity junctions, and shorter ohmic contacts at the contact holes, resulting in a smaller ohmic contact. It becomes bigger. In general, an increase in contact resistance causes problems such as cross talk, RC time delay, and power consumption.

Meanwhile, in order to solve the problems of the aluminum wiring, a method of using a barrier metal as a diffusion barrier between the aluminum conductor and the silicon substrate has been proposed. This diffusion barrier film should not react with a conductive wire (eg aluminum) or a substrate (eg silicon), should have good adhesion characteristics, have low contact resistance, and have high electrical and thermal conductivity.

As an example of the diffusion barrier layer that satisfies the above characteristics, a conventional metal wiring forming method will be described using a titanium / titanium nitride layer (Ti / TiN). A method of manufacturing a semiconductor device using this titanium / titanium nitride film as a diffusion barrier is shown in FIGS. 1A to 1D.

Referring to FIG. 1A, a device isolation region is defined by a field oxide film 20 on a semiconductor substrate 10, and impurities are implanted into the substrate 10 to form a source / drain region 30. Subsequently, an insulating film on which a contact is to be formed, for example, an oxide film 40 is grown.

Referring to FIG. 1B, a contact opening h is formed by etching the oxide layer 40 by a photolithography process.

Referring to FIG. 1C, titanium, which is in ohmic contact with the source / drain region 30, is sputtered into the contact hole on the oxide layer 40 to a thickness of 300 to 900 kPa. Vapor deposition to form a titanium film 50 as an ohmic layer, and then titanium nitride is deposited on the titanium film 50 to a thickness of 600 to 2000 microseconds by the same sputtering method to form a titanium nitride film 60 as a diffusion barrier. To form.

Referring to FIG. 1D, conductive may be deposited on the deposited titanium nitride layer 60, for example, to form the wiring layer 70.

Reference numeral 65 denotes pores formed by poor step coatability.

For example, a titanium / titanium nitride film has a poor step coverage as the aspect ratio of the contact opening increases. The voids 65 are formed at the contact openings, and the pores cause short circuits of the wirings, thereby reducing the reliability of the device. Recently, a sputtering method using a collimator has been studied, but this method is also difficult to bury a contact without pores due to an increase in the aspect ratio of the contact opening due to a decrease in contact size. Therefore, there is a need to switch to a chemical vapor deposition (CVD) method having excellent step coverage.

In recent years, in order to solve the problem of step coverage as described above, a method of depositing a tungsten nitride film as a diffusion barrier film using a plasma chemical vapor deposition method has been proposed. In particular, by using the chemical vapor deposition method, it is possible to improve the step coverage property and to reduce the contact resistance as compared with the case of using the titanium nitride film by using a tungsten nitride film having a low resistivity as the diffusion barrier. (The specific resistance of the tungsten nitride film is 30 to 100 µmΩ and the specific resistance of the titanium nitride film is 200 to 700 µm .. 93-24105 (Inventor: Min Seok-ki and one other person).

However, according to the above method, even though the resistivity of the tungsten nitride film is lower than that of the titanium nitride film, the tungsten nitride film does not make ohmic contact with the silicon substrate, resulting in a higher contact resistance.

The contact characteristics of the silicon substrate 10 and the metal layer 70 are shown in FIGS. 2A and 2B.

The contact property between the silicon substrate 10 and the metal layer 70 is applied to the silicon substrate 10 and the metal layer 70 by applying a voltage, for example, -5V to + 5V, and measuring resistance and current at both ends thereof. It is obtained by showing the resistance value and the current value corresponding to each voltage on the graph.

2A is a graph showing ideal ohmic contact characteristics. Two materials, for example, that metal and semiconductor have ohmic contact properties means that both materials have linear voltage (V) -current (1) properties. In the case of the ideal ohmic contact, the voltage-residual characteristic increases as the voltage increases, the current increases with the slope of 1 / resistance (1 / R) in both directions (+,-) (see line) and has a constant resistance (see See helix).

2B is a graph showing the results of measuring contact characteristics between the tungsten nitride film and the n ⁺ substrate in accordance with the above method. First, the voltage-current characteristic does not have a constant slope as in the ohmic contact characteristic, and in the negative voltage, the current increases in a parabolic shape, and in the positive voltage, as the voltage increases. The current decreases parabolic (see polyline). As a result, it can be seen that the resistance appears to be inconsistent in the voltage-resistance characteristic (see line).

As described above, when the metal and the semiconductor do not have the ohmic characteristic, that is, the linear characteristic of the voltage-current, the contact resistance is increased. As described above, such an increase in contact resistance causes problems such as semiconductor device cross talk, RC time delay, and power consumption.

Accordingly, an object of the present invention is to provide a more reliable method for forming a semiconductor device metal wiring by reducing the contact resistance when using a tungsten nitride film using the plasma chemical vapor deposition method having excellent step coverage as a diffusion barrier.

To achieve the above object, the present invention comprises the steps of depositing titanium in the contact openings on the silicon substrate to form a titanium film; Performing NH ₃ plasma treatment after forming the titanium film; It provides a method for forming a conductive element metal wiring comprising the step of depositing tungsten nitride by chemical vapor deposition method on the NH ₃ plasma treated titanium film.

The process may further include a process of depositing a metal on the deposited tungsten nitride film to form a metal layer and heat treating the metal layer to reflow. The metal is selected from the group consisting of aluminum (Al), aluminum alloy, copper (Cu), gold (Au), silver (Ag), molybdenum (Mo), cobalt (Co) and tungsten (W), The aluminum alloy uses aluminum-1% silicon or aluminum-0.5% copper-1% silicon.

The chemical vapor deposition method used to form the tungsten nitride film is a plasma chemical vapor deposition method. In addition, the NH ₃ plasma treatment is performed at a deposition temperature of 300 to 400 ° C., an RF power of 90 to 110 W, a deposition pressure of 0.05 to 0.15 Torr, preferably a deposition temperature of 350 ° C., an RF power of 100 W, and 0.1 Torr. Carry out under deposition pressure. The tungsten nitride film is formed under a deposition temperature of 200 to 450 ° C., an RF power of 30 to 400 W, and a deposition pressure of 0.05 to 0.3 Torr. Preferably, the tungsten nitride film has a deposition temperature of 350 ° C. and an RF of 100 W as in the NH ₃ plasma treatment. It is formed under a deposition pressure of power of 0.1 Torr. The size of the contact opening is preferably formed to be 0.25μm or more. When forming the tungsten nitride film, the contact opening may be buried with the tungsten nitride (see FIG. 8). In this case, the size of the contact opening is preferably 0.25 μm or less. When the titanium film is formed, the titanium film may be formed only at the bottom of the contact opening (see FIG. 9), and after the titanium film is formed, the titanium film is deposited to fill the contact opening with tungsten nitride, and then etch back is performed. Metal wiring with low resistivity may be deposited to form metal wiring (see FIG. 10). In addition, the contact opening may be buried with the tungsten nitride, and the tungsten nitride film may be used as a wiring layer (see FIG. 11). It can also induce a reaction.

According to the present invention, a silicon film and a titanium film exhibiting ohmic properties are deposited before the tungsten nitride film is deposited by plasma chemical vapor deposition, and a tungsten source gas (eg, WF ₆ , hereinafter referred to as WF ₆ ) which is essentially used for the deposition of the tungsten nitride film. ) and the titanium (and Ti) titanium fluoride La (the TiF ₃ produced by the reaction of the film) to obtain a low contact resistance by suppressing the film generated by the NH ₃ plasma processing.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

3A to 3F show a first embodiment for explaining a metal wiring forming method of a semiconductor device according to the present invention, wherein like reference numerals in the drawings denote like materials.

3A is a cross-sectional view showing a step before forming a contact opening. The field oxide film 20 is grown in a device isolation region on the silicon substrate 10 by a conventional method, and impurities are implanted into the substrate 19 to form a source / drain region 30, and then the source / drain An insulating film, for example, an oxide film 40 is grown over the region 30. The field oxide film 20 is grown to a thickness of 3000 to 4000 GPa, the oxide film 40 is grown to 12000 GPa, and the impurities include n-type impurities such as phosphorus (P), arsenic (As), boron (B), and the like. The same p-type impurity is used.

3B is a cross-sectional view illustrating a step of forming a contact opening h in the insulating film. A photoresist is applied on the oxide film 40 and exposed and developed to form a photoresist pattern (not shown). Subsequently, the oxide layer 40 is etched by reactive ion etching (RIE) using the photoresist pattern as an etching mask to form the opening h. The width of the opening is formed to be 0.25μm or more to connect the silicon substrate and the aluminum wiring.

3C is a cross-sectional view illustrating a step of forming an ohmic layer 50 on the insulating layer 40. Titanium is deposited on the etched insulating film 40 to a thickness of 200 to 1000 Å by sputtering to form an ohmic layer, for example, a titanium film 50. The titanium film 50 is preferably deposited to a thickness of 800 Å so as to have ohmic contact characteristics with the silicon substrate 30.

3d is a cross-sectional view showing a step of performing NH ₃ plasma treatment on the deposited titanium film 50. In a subsequent process, the TiF ₃ compound produced by combining WF ₆ source gas used to form the tungsten nitride film with the deposited titanium film 50 increases the contact resistance. NH ₃ is introduced into a chamber in a nitrogen atmosphere and separated into N ⁺ , 3H ⁻ , and the N ⁺ ions react with the titanium film 50 to form titanium nitride, and the F of the WF ₆ gas injected in a subsequent process Ring reaction with Ti to inhibit the production of TiF ₃ . Reference numeral 55 denotes a plasma state of HN ₃ . The NH ₃ plasma treatment is carried out in the same chamber as the chamber in which the tungsten nitride film deposition process, which is a subsequent process, is carried out under a deposition temperature of 300 to 400 ° C., an RF power of 90 to 110 W, and a deposition pressure of 0.05 to 0.15 Torr. . Preferably it is carried out at a deposition temperature of 350 ℃, RF power of 100W, deposition pressure of 0.1 Torr. Result according to the embodiment whether the NH3 plasma process that is, represents a cross-sectional SEM photograph of the case is not conducted in the case subjected to the NH ₃ plasma process in Fig claim 5a also and the 5b, compared to the data of the contact resistance distribution of the 6a also and the 6b is shown.

3E is a cross-sectional view showing the step of forming the diffusion barrier 63. The NH ₃ plasma treated data is shown in FIGS. 6a and 6b.

3E is a cross-sectional view showing the step of forming the diffusion barrier 63. Tungsten nitride is deposited on the NH ₃ plasma treated titanium 53 by chemical vapor deposition, for example, plasma enhanced chemical vapor evaporation (PECVD) to form a tungsten nitride layer 63 as a diffusion barrier.

The tungsten nitride film 63 is deposited to have a deposition thickness of 50 to 1000 Pa at a deposition temperature of 200 to 450 ° C., an RF power of 30 to 400 W, and a deposition pressure of 0.05 to 0.3 Torr. Preferably, as in the formation of the titanium film 50, it is carried out at a deposition temperature of 350 ℃, FR power of 100W, deposition pressure of 0.1 Torr.

If necessary, after the deposition of the tungsten nitride film 63, heat treatment is performed at a temperature of 400 ° C. or higher to oxidize the tungsten nitride film 63 and the silicon in the source / drain region 30 and the titanium in the titanium film 50. And may induce the reaction to form titanium silicide.

3F is a cross-sectional view showing the step of forming the wiring layer 70. A metal layer is formed on the tungsten nitride film 63 by sputtering to form a metal layer, and then the metal is heat-treated in vacuum at a high temperature below the melting point to reflow to form a wiring layer 70 to bury the contact without pores. . As the metal, for example, an aluminum alloy containing a silicon component such as aluminum-1% silicon or aluminum-0.5% copper-1% silicon is used.

4 is a result of measuring the contact characteristics between the titanium film and the n ⁺ region of the silicon substrate, and the contact characteristics were measured in the same manner as the method described with reference to FIGS. 2a and 2b. The current-voltage characteristic was linear as shown by the ideal ohmic characteristic in FIG. 2a (see line), and the resistance also showed a constant value as shown by the ideal ohmic characteristic (see line). The slope of the spiral is the inverse of the resistance.

Therefore, it can be seen from the above specific result that the titanium film 50 and the silicon substrate 30 are in ohmic contact.

5a 5b and the second is a turning in the NH ₃ plasma process step of the embodiment of the process, compared to the contact gigubuyi cross section according to the NH3 plasma processing oil, non-SEM picture.

FIG. 5A is a SEM photograph showing a cross section of a contact opening obtained by depositing tungsten nitride at a thickness of 900 kPa without performing NH ₃ plasma treatment after depositing titanium at a thickness of 300 kPa. It is shown that a TiF ₃ layer formed by the chemical reaction between gas (WF ₃ ) and the deposited titanium (Ti) is formed between the titanium film (Ti) and the tungsten nitride film (WN _x ).

FIG. 5b is a SEM photograph showing a cross section of a contact opening obtained by depositing the titanium to a thickness of 300 kPa and performing NH3 plasma treatment according to the method of Example 1, and depositing tungsten nitride to a thickness of 900 kPa. It is shown that no film is formed at the interface between the titanium film and the tungsten nitride film.

6A to 6B also show the distribution of contact resistance with and without the NH ₃ plasma treatment in the NH ₃ plasma treatment step of the above embodiment. That is, it shows the effect of the TiF ₃ layer on the contact resistance.

The contact resistance is obtained by measuring contact layer resistance existing in series on one metal line, and dividing the measured total resistance by the total number of contacts.

FIG. 6A shows that the contact sizes are 0.44 x 0.52 µm 2 (see line a) when the NH ₃ plasma treatment is not performed. 0.6 / 0.8㎛ ² (see line b), it shows the distribution of the contact resistance when the 1.0 / 1.0㎛ ² (see line c).

When the contact size is large (see line c), the contact resistance is distributed almost uniformly from 0Ω to 500Ω, but as contact size decreases (see line a and b), the contact resistance is widely distributed over 1000Ω to 5000Ω. It can be seen.

6B shows that the contact sizes are 0.45 / 0.55 μm ² (see line d), 0.5 / 0.6 μm ² (see line e), and 0.6 / 0.7 μm ² (see line f) when NH ₃ plasma treatment is performed. , Shows the distribution of contact resistance at 0.1 / 1.0 μm ² (see g line).

First, the contact resistance is almost uniformly distributed in the case where the contact size is small or the contact size is large.

Comparing the contact resistance in the case of thin or similar contact sizes with FIG. 6a, the contact resistance in the case where the contact size is large has an approximate value in FIG. 6a, but the contact resistance in the case where the contact size is small is much smaller than that in FIG. Could know. (Note that the two graphs have different resistance ranges in reference to the two graphs above.) For example, lines c of FIG. 6a and gb of FIG. 6b having the same contact size (1.0 / 1.0 µm ² ) are 200! It has a contact resistance of 300 mA. If so, comparing the size of the similar contact line 6a degree a (0.44 / 0.52㎛ ²⁾ and the d-line 6b-degree (0.45 / 0.55㎛ ²⁾ a line has a large contact resistance is distributed between 2000~5000Ω d The line has a small contact resistance distributed between 325 and 375 kΩ. In conclusion, the contact resistance in the case of NH ₃ plasma treatment has a much lower contact resistance than the case in which the NH ₃ plasma treatment is not performed, and the distribution thereof is uniform.

7A to 7B show results of a device war reliability test using a wiring of a titanium / tungsten nitride film / aluminum structure.

The reliability test was performed for 48 hours at a high temperature storage test (HTS; high temperature storage) at a temperature of 450 ° C., and tested the reliability of the titanium film 50 and the tungsten nitride film 63 by applying poor conditions to the device. Assumptions are known as general conditions. The first point on the graph is a result of alloying a device having a conventional titanium / titanium nitride film / aluminum structure at a temperature of 400 ° C. for 30 minutes, and the second point is a titanium / titanium according to the present invention. The device having the tungsten nitride film / aluminum structure wiring layer was also a result of alloying at a temperature of 400 ° C. for 30 minutes. The third to sixth points show the results after the tests were conducted for 6 hours, 12 hours, and 48 hours, respectively, at a temperature of 450 ° C.

FIG. 7A is a result of measuring contact resistance of devices having different contact sizes. The measurement under contact tablet proceeded in the same manner as presented with respect to Figures 6a and 6b.

The contact resistance specification of the tested device is 500 [µs / Contact] or less, and in Fig. 7a, the contact size is 0.36 / 0.44µm ² [see line i], 0.40 / 0.48 ² (see line j), 0.44 / 0.52µm ² ( reference line k), see 0.6 / 0.68㎛ ² (l line), see 0.1 / 0.1㎛ ² (m-line) it is contact resistance are shown in the case of. The contact resistors shown in FIGS. 3-6 were not different from the alloy results of the conventional structure (see point 1) or the alloy results of the structure according to the present invention (see point 2). Both exhibit good characteristics within the standard.

7B shows the result of measuring leakage current in the impurity contact region.

The leakage current is obtained by applying a voltage between the semiconductor substrate 10 and the wiring layer 70 and measuring the current at both ends. For example, when the source / drain region 30 is n ⁺ and the semiconductor 0 substrate 10 is p type (n ⁺ / p structure), 5V is applied between the semiconductor substrate 10 and the wiring layer 70. In the case where the source / drain region 30 is p ⁺ and the semiconductor substrate 10 is n-type (p ⁺ / n structure), -5V is applied between the semiconductor substrate 10 and the wiring layer 70 to reduce leakage current. Measure

The specification limit for leakage current is 1xe-15 [A / μm] for the tested device, as shown in Figure 7b, with the results measured in the n ⁺ / p structure (see line n), p ⁺ / n The results measured in the structure (see p) all met the specification.

Good results of the reliability test show that the diffusion barrier of the device manufactured according to the present invention can serve as a diffusion barrier even under poor conditions.

Example 2

Exemplary embodiments of the present invention are the same as those of the first embodiment except that the diffusion barrier layer 66 is buried in the tungsten nitride to form the diffusion barrier layer 66 when the diffusion barrier layer 63 of FIG. 3e is formed.

FIG. 8 is a cross-sectional view illustrating a second embodiment of the present invention, in which the ohmic layer 50 and the tungsten nitride nitride contact are buried to form a diffusion barrier 66, and then formed on the diffusion barrier 66 It is sectional drawing which shows the process of depositing a metal and forming the wiring layer 76. FIG.

Example 3

In the first embodiment, the present embodiment is the same as the first embodiment except that the ohmic layer 50 is formed by depositing the titanium only on the bottom portion of the contact opening h when the ohmic layer 50 of FIG. 3c is formed. Proceed with the method.

FIG. 9 is a cross-sectional view showing a third embodiment of the present invention. In the formation of the titanium film 59, the titanium is deposited only on the bottom portion of the contact opening h to form an ohmic layer 57, and the ohmic layer Tungsten nitride is deposited on the 57 to form the diffusion barrier 67, and then metal is deposited on the diffusion barrier 67 to form the wiring layer 76.

Example 4

In the third embodiment, the present embodiment proceeds in the same manner as in the third embodiment except that the diffusion barrier layer 68 is buried in the tungsten nitride to form the diffusion barrier layer 68 when the diffusion barrier layer 67 of FIG. 9 is formed.

10 is a cross-sectional view showing a fourth embodiment of the present invention, in which the tungsten nitride is deposited on the ohmic layer 57 to bury the contact to form a diffusion barrier (not shown), and the oxide film 40 ) Is a cross-sectional view showing a process of etching back to expose the contact openings with tungsten nitride to form a diffusion barrier film 68 and then depositing metal to form the eight wiring layer 78.

Example 5

In the first embodiment, when the diffusion barrier layer 63 of FIG. 3e and the wiring layer 70 of FIG. 3f are formed, the contact is buried with tungsten nitride used to form the diffusion barrier layer 63 to form the diffusion barrier layer 69. Except for forming the wiring layer 69, the present embodiment proceeds in the same manner as in the first embodiment.

FIG. 11 is a cross-sectional view showing a fifth embodiment of the present invention, in which the tungsten nitride is deposited thickly on the sacks ohmic layer 53 to bury 8 contacts to form a diffusion barrier film 69 and at the same time the wiring layer 69 It is sectional drawing which shows the process of forming a metal.

As described above, according to the present invention, before depositing the tungsten nitride film by the plasma arc deposition method, the silicon substrate and the ohmic layer titanium are deposited and NH ₃ plasma treatment is performed to provide excellent step coverage and pores. It is possible to form a reliable metal wiring with low contact resistance as well as contactless free buried.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical idea to which the present invention pertains.

Claims (16)

Depositing titanium in the contact opening on the silicon substrate to form a titanium film; Performing NH ₃ plasma treatment on the titanium film formation; And depositing tungsten nitride by chemical vapor deposition on the NH ₃ plasma treated titanium film to form a tungsten nitride film. The method of claim 1, further comprising depositing a metal on the tungsten nitride layer to form a metal layer, and heat treating and reflowing the metal layer. The method of claim 2, wherein the metal is composed of aluminum (Al), aluminum alloy, copper (Cu), gold (Au), silver (Ag), molybdenum (Mo), cobalt (Co) and tungsten (W). The semiconductor device metal wiring forming method, characterized in that any one selected from the group. 4. The method of claim 3, wherein the aluminum alloy is aluminum-1% silicon or aluminum-0.5% copper-1% silicon. The method of claim 1, wherein the chemical vapor deposition method is a plasma chemical vapor deposition method. The method of claim 1, wherein the NH ₃ plasma treatment is performed at a deposition temperature of 300 to 400 ° C., an RF power of 90 to 110 W, and a deposition pressure of 0.05 to 0.15 Torr. The method of claim 6, wherein the deposition temperature is 350 ° C., the RF power is 100 W, and the deposition pressure is 0.1 Torr. The method of claim 1, wherein the tungsten nitride film is formed at a deposition temperature of 200 to 450 ° C., an RF power of 30 to 400 W, and a deposition pressure of 0.05 to 0.3 Torr. The method of claim 8, wherein the deposition temperature is 350 ° C., the RF power is 100 W, and the deposition pressure is 0.1 Torr. The method of claim 1, wherein the contact opening has a size of 0.25 μm or more. The method of claim 2, wherein the contact opening is buried with the tungsten nitride when the tungsten nitride film is formed. 12. The method of claim 11, wherein the contact opening has a size of 0.25 µm or less. The method of claim 2, wherein the titanium film is formed only at a bottom portion of the contact opening when the titanium film is formed. 15. The method of claim 13, wherein after the tungsten nitride film is deposited, an etch back of the tungsten nitride film is applied to bury a contact opening in the tungsten nitride film. 2. The method for forming a semiconductor device metal wiring according to claim 1, wherein the contact opening is buried in fructose tungsten nitride and the tungsten nitride film is used as a wiring layer. The method of claim 1, further comprising performing heat treatment at a temperature of 400 ° C. or higher after depositing the tungsten nitride film.