JPH03286532A - Formation of passivation film in plasma cvd apparatus - Google Patents

Abstract

PURPOSE:To produce a passivation film provided with an internal stress which prevents an aluminum interconnection from being deteriorated by a method wherein a reaction process is executed at a plasma CVD apparatus by setting a first combination, a second combination or a third combination regarding a reaction gas system and a high-frequency power-supply frequency so as to correspond to the production speed and the film quality of the passivation film. CONSTITUTION:At a first combination (SiH4-N2: 50kHz), a second combination (SiH4-NH3: 50kHz) and a third combination (SiH4-NH3; 13.56MHz) regarding a reaction gas system and a high-frequency power-supply frequency, there exists an interrelationship in which a slow production speed or a fast production speed according to this order corresponds to the low closeness or the high closeness of a film quality and to the small content or the large content of hydrogen. When an aluminum interconnection is thin, the slow production speed is permitted and the film quality by the high closeness and by the small content of hydrogen is obtained by using the first combination. On the contrary, when the interconnection is thick, a productivity is enhanced by the third combination of the slow production speed.

Description

[Detailed Description of the Invention] [Field of Application in M Business] The present invention relates to a method for forming a passivation film in a plasma CVD apparatus, and more specifically, to prevent deterioration of aluminum wiring due to internal stress of the passivation film,
In addition, it is a method for obtaining as good a film quality as possible in consideration of productivity.

[Prior Art] In the manufacture of semiconductor IC devices, there is a process of forming a thin film on the surface of a silicon wafer.

FIG. 5 shows an example of the basic structure of a silicon wafer 1 on which a thin film is formed. First, a silicon oxide film 1b is formed on the surface of a silicon substrate 1a, and is etched into a predetermined pattern. Next, aluminum wiring lc is connected to the p layer and n- layer of the substrate 1a through the gap in the silicon oxide film 1b, and these are connected to the outside. Next, a passivation film 1d is formed on the surfaces of the silicon oxide film 1b and the aluminum wiring IC to protect them. As a passivation film, silicon nitride (Si3
N4) has good performance, and the patent publication rG
No. 3-184340, "Semiconductor Device" has been disclosed and put into practical use.

Chemical vapor deposition (CVD) is generally used to produce thin films.
However, recently, conventional atmospheric pressure CV
A plasma CVD apparatus has been developed that has the advantage of being able to perform a reaction process at a lower temperature than the D apparatus.

FIG. 6 shows a cross section of the basic configuration of the plasma CVD apparatus 2. As shown in FIG. A substrate la to be processed is placed on a sample stage 2b provided inside a reactor 2a, and heated by a heater 2C. A shower electrode 2d is provided above the sample stage 2b, and a reaction gas is pressurized through an inlet 2e and injected through a number of small holes provided in the shower electrode 2d. The injected reaction gas is turned into plasma by applying high frequency power from the power source 2f between the shower electrode 2d and the sample stage 2b. The energy of atoms or electrons in the plasma-formed reaction gas is higher than that in the case of being excited by temperature, making it easier to react, so an effective reaction process can be carried out at a relatively low temperature.

[Problem to be solved] Internal stress occurs in the passivation Mid formed as described above, and the aluminum wiring IC that is in close contact with this generates internal stress.
Pressure is applied to Recently, as the degree of integration of IC devices has improved, aluminum wiring ICs have become extremely thin, so when this internal stress is large, a deterioration phenomenon called voids occurs. Therefore, it is necessary to reduce this internal stress by some method.

However, the condition is that the film quality is as good as possible. However, from the viewpoint of productivity, there are no published papers or materials regarding internal stress and film quality depending on production conditions. On the other hand, the inventor of the present invention conducted systematic experiments on the internal stress and film quality of a silicon nitride passivation film using the experimental design method from the viewpoint of productivity.

In the above experiments, monosilane (S i H4) + xx gas (N2
) gas system, or monosilane + ammonia (NH3
) gas system, and the frequency of the high frequency power source is a relatively low frequency of 50 kHz, or a relatively high frequency of 13.
56 MHz was used in appropriate combination. According to the results, it was found that the internal stress characteristics of silicon nitride films depend on reaction parameters such as generation temperature, generation pressure, and gas flow rate in the reaction process, and that there is a correlation among them. Therefore, by controlling the reaction parameters, it is possible to obtain a desired internal stress within a certain range. At the same time, it was found that each method has a clear correlation with the denseness of the produced passivation film, the film quality depending on the hydrogen content, and the production rate. Since the production speed directly affects productivity, there is a need for a method that takes these factors into account and produces a passivation film of the highest possible quality and productivity without deteriorating the aluminum wiring. Conceivable.

This invention was made in view of the above, and
The purpose of this invention is to provide a method for producing a passivation film that satisfies the above conditions for the D device.

[Means for Solving the Problems] The present invention is a method for producing a silicon nitride (S 13N4) passivation film for a silicon oxide film and aluminum wiring formed on a silicon wafer using a plasma CVD apparatus.

For the plasma CVD equipment, the first combination of the reaction gas system and the frequency of the high-frequency power supply (SiH4N2.50 k
HZ), or the second combination (S iH+
-NH3, 50kHz), or a third combination (
S i H4-NH3, 13, 58 MHz) to perform the reaction process. In order to prevent the deterioration of aluminum wiring due to the internal stress of the passivation film, we appropriately control the generation temperature, generation pressure, and gas flow rate of the reaction parameters of each reaction gas system to prevent internal stress from deteriorating the aluminum wiring. Generate a passivation film with

In the above, the first frequency of the reaction gas system and the high frequency power supply is
, in the order of the second and third combinations, due to the correlation between the slow to fast formation rate of the passivation film, the high to low density of the film quality, and the low to high hydrogen content, the first
, select and set one of the second and third combinations.

In addition, each element of the reaction parameter is determined by the correlation between the generation temperature of the reaction parameter elements, high to low, and the generation pressure and gas flow rate, which correspond to the strong to weak internal stress of the passivation film. They are controlled respectively.

[Function] In the above method for forming a passivation film, the reaction parameters are controlled according to the thickness of the aluminum wiring formed on the silicon wafer, and when the thickness is thin, the internal stress is reduced; If the thickness is large, increase the internal stress.

In either case, deterioration of the aluminum wiring can be avoided and the passivation film can be replaced with as high a quality as possible. Here, the first combination (S i H4-N2 ° 50 kHz), the second combination (SiH4-NH3, 50 kHz), and the third combination (S i H4-NH3, 13,5
6MHz), the generation speed is slow to fast according to this order,
There is a correlation between high to low film density and low to high hydrogen content, so when the thickness of aluminum wiring is thin, the first
By combining these, a film quality with high density and low hydrogen content can be obtained. On the other hand, when the wiring is thick, the third combination, which has a faster generation speed, improves productivity. However, in this case, the required conditions are satisfied even if the density and hydrogen content are slightly lower f. Furthermore, when the thickness of the interconnect is between the above, the second combination is used to generate a passivation film with intermediate generation rate, density, and hydrogen content.

In this way, deterioration of the aluminum wiring can be prevented, and a passivation film of as high quality as possible can be produced with commensurate productivity according to the requirements of the IC device.

[Example 1] Figures 1, 2, and 3 show experimental data that form the basis of a method for forming a passivation film in a Lufrazma CVD apparatus according to the present invention. In each figure, the first combination of frequencies of the reactant gas system and the high-frequency power source (S 1H
4-N2.50kHz) as a landmark, select the second combination (
SiH4-NH3゜50kHz) is marked with Δ, and the third introduction (S i H4-NH3,13,56MHz
) with the mark. The internal stress S on the vertical axis in each figure is defined as compressive stress and tensile stress depending on the force received by the other side. Compressive stress exerts a compressive force on the wafer and has a single sign, and tensile stress exerts a tensile force and has a ten sign. It is expressed as.

Figure 1(a) shows the relationship between the internal stress S and the formation temperature t, and for the first and second combinations, when t is ~200'C or less, S (absolute value, below) is quite small; When t exceeds this, it increases. On the other hand, in the third combination, S, which depends on t, is relatively small. Figure (b) shows the internal stress S with respect to the generated pressure p, and in the first and third cases, p is ~1
．． O(T.

S is small below rr), and increases rapidly or gradually above this. Figure (c) shows the flow rate q of the reaction gas (siH4)
q is ~50 (
SCCM) or less, S is small, and beyond this, the first increases rapidly, and the second and third increase gradually. Due to the above, the first
In the combination, the change in S is generally rapid, but it is simple and easy to control. It is also clear that the third change does not depend greatly on the reaction parameters, and that some of the second changes are not simple.

Next, FIG. 2(a) shows the internal stress S versus the etch rate r. Here, the etch rate r represents the etching rate when the produced film is etched by an appropriate method, and the smaller r is, the higher the density and the better the quality. According to the figure, it can be seen that within a certain range of S, the first combination has the highest density, and the second and third combinations have successively lower density. Figure (b) shows the internal stress S versus hydrogen content QH.

It is clearly observed that the lower the QH, the better the quality, so the first one is the best quality, decreasing in order to the second and third.

Next, data on the film formation rate V is shown in FIG.

The first combination is a wide range of S with V of 300 to 85.
They are concentrated in the range of 0 (angstroms/m1n), and the smaller S is, the larger V is, but the deviation is small. Second
In the third case, the relationship between S and V is almost random, and V is often larger than in the first case.

Although the above experimental data is aggregated, it is difficult to derive a numerical correlation beyond this. Therefore, the correlation between the trends of each element is shown in a table in FIGS. 4(a) and 4(b). Diagram (a)
indicates the state of film formation using the first, second, and third combinations of reaction gas system and frequency, and for each formation method, the formation speed V is slow to fast, and the density d is high to low. , and the hydrogen content Q■ corresponds to a small to a large amount. Figure (b) shows the correlation of internal stress S with respect to changes in the reaction parameters of production temperature t1 production pressure p and gas flow rate q, and is similar to that described above.

The above correlation and experimental data are used in the production of pudgebage excreta. First, for IC devices that require thin aluminum wiring and high-quality films, the first combination is adopted, as shown in Figures 1(a) and (b).
) and (c) according to reaction parameters (t, I), Q
) to make the internal stress S a small value that does not deteriorate the aluminum wiring. In this case, Fig. 2 (a), (b)
As a result, a film with high density d and low hydrogen content QB can be obtained. However, since the production speed is slow, productivity is unavoidably low. On the other hand, if the aluminum wiring is thick and productivity is more important than film quality, the third combination with the fastest generation rate V is selected and the reaction parameters are controlled to provide an appropriate internal stress S. In this case, the film quality is generally at the lowest level. Moreover, for intermediate values between these, the corresponding generation state can be changed by taking the second combination.

[Effects of the Invention] As is clear from the following explanation, in the method for producing a passivation film according to the present invention, plasma CVD is
Experiments were conducted on the device using three combinations of reaction gas system and high-frequency power supply frequency, and analysis of the obtained data revealed the internal stress of the passivation film in relation to reaction gas generation temperature, generation pressure, and gas flow rate. The correlation between the density of the produced film and the hydrogen content for three types of combinations was found in detail, and based on this, it was possible to control the internal stress to an appropriate value by controlling the reaction parameters to prevent the deterioration of aluminum wiring. In cases where film quality is more important, productivity is more important, or an intermediate case, one of three combinations of the frequencies of the reaction gas system and high frequency power source is appropriate. It satisfies the required conditions and has a great effect in providing a rational method for producing a passivation film.

[Brief explanation of drawings]

Figure 1 (a), (b), (c), Figure 2 (a), (b)
), and FIG. 3 shows plasma CVD according to the present invention.
Figures 4(a) and 4(b) are diagrams showing experimental data that form the basis of the method for producing a passivation film in the device.
FIG. 5 is a cross-sectional view showing an example of the basic structure of a silicon wafer on which a thin film is formed; The figure is a sectional view of a plasma CVD apparatus. DESCRIPTION OF SYMBOLS 1... Silicon wafer, 1a... Substrate, 1b... Silicon oxide film, 1c... Aluminum wiring, ld... Passivation film, 2... Plasma CVD equipment ft, 2a... reactor, 2
b...Sample stand, 2c...Heater 2d.
... Shower N pole, 2e ... Inlet, 2f
...power supply, S...internal stress, t...generation temperature, p.
...Generation pressure, q...Gas flow rate, r...
Etch rate, Q■...Hydrogen content, ■...Generation rate. Figure 4 (a) (b)

Claims (3)

[Claims] (1) In the production of a silicon nitride (Si_3N_4) passivation film for a silicon oxide film and aluminum wiring formed on a silicon wafer using a plasma CVD apparatus,
The first combination (SiH_4-N_2, 50kHz), the second combination (SiH_4-NH_3, 50kHz), or the third combination of the frequencies of the reaction gas system and the high-frequency power supply correspond to the generation rate and film quality of the passivation film. Combination (SiH_4-NH_3, 13.5
6MHz) to perform the reaction process,
In order to prevent the deterioration of the aluminum wiring due to the internal stress of the passivation film, the internal stress is prevented by appropriately controlling the generated humidity, the generated pressure, and the gas flow rate of the reaction parameter elements of each of the reactive gas systems. producing the above passivation film having
A method for producing a passivation film in a plasma CVD apparatus. (2) In order of the first, second, and third combinations of the frequencies of the reaction gas system and the high-frequency power source, the generation rate of the passivation film is slow to fast, the denseness of the film quality is high to low, and 2. The method for producing a passivation film in a plasma CVD apparatus according to claim 1, wherein one of the first, second, and third combinations is selected and set based on a correlation corresponding to a low to high hydrogen content. (3) Due to the correlation between the generation temperature of the reaction parameter elements, which corresponds to the strength and weakness of the internal stress of the passivation film, and the generation pressure and gas flow rate,
3. A method for producing a passivation film in a plasma CVD apparatus according to claim 1 or 2, wherein each element of said parameters is controlled respectively.