JPH0831814A - Method for forming Si oxide film and semiconductor device - Google Patents

Abstract

(57) [Summary] [Structure] Organosilicon compounds react with ozone to produce Si
This is a CVD method for forming an oxide film, which is composed of initial low-pressure Si oxide film growth and subsequent high-pressure Si oxide film growth. [Effect] It is possible to form a planarized interlayer insulating film having a flow property that does not depend on the underlying layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a Si oxide film by a chemical vapor deposition method and a semiconductor device having a multilayer wiring structure to which the Si oxide film is applied.

[0002]

2. Description of the Related Art Since the problem of base dependency in the TEOS-O ₃ CVD method was reported in 1989, its solution has been studied. And the Journal of Electrochemical Society (J. Electrochem. Soc.),
Vol.138, No.2 (1991), pp.550-554, plasma pretreatment method, JP-A-3-198340, method for pre-forming low concentration ozone film, Japanese journal
Of Applied Physics (Jpn. J. Appl. Phi
s.), Vol.32 (1993), pp.L110-L112, a surface treatment method with an organic agent has been proposed as a method for eliminating the dependency on the substrate, but the instability of these effects and the influence of the substrate pattern have been proposed. The problem of is not solved, and it remains as an issue.

[0003]

The problem to be solved by the present invention is that the surface shape of the growth film has irregularities or the growth rate changes depending on the material and surface condition of the underlying material. To solve.

[0004]

[Means for Solving the Problems] The above-mentioned problems are solved in the initial stage of thermal CVD using an organic Si compound and ozone (O ₃ ).
This can be solved by performing a short-time growth of about 30 seconds or more at a low pressure of Pa or less.

[0005]

The above-mentioned means suppresses the reaction of the introduced reaction gas in the gas phase, and works so that the growth reaction on the substrate surface mainly proceeds. Therefore, the concentration of the reaction product generated in the gas phase reaction is suppressed to a low level to reduce its influence, and ozone, which is an oxidant, is further transported to the surface, and acts to promote oxidation on the surface. As a result, the dependency on the underlayer is eliminated, and the semiconductor device having the multilayer wiring formed by using this CVD method is also realized.

[0006]

【Example】

(Example 1) A first example in which an organic silicon compound and ozone are reacted to form a Si oxide film having no underlying dependency will be described. Here, the case where tetraethyl orthosilicate (TEOS) is used as the organic silicon compound will be described.

The pressure change, which is a characteristic of the pressure-combined CVD method proposed this time, arrived from the examination under various conditions will be described with reference to FIG. The substrate is inserted at point A when the CVD reaction chamber is evacuated, and after the transfer operation is completed, N ₂ of carrier gas is introduced at point B to keep the pressure at a predetermined low pressure.
At the point C where the pressure is stable, TEOS is introduced, and at the point D where the flow rate is stable, O ₂ containing high concentration O ₃ is flowed to start the growth.
After the initial low-pressure growth between DEs, the vacuum exhaust amount is reduced to change the pressure in the reaction chamber to the high-pressure point F. Main growth was performed between the high pressure FGs, the supply of the reaction gas was stopped at the point G, the vacuum was drawn, and then the substrate was taken out at the point H.

Next, the relationship between the pressure and time relating to the growth of DE in the initial stage and the dependency on the base, and the relationship between the pressure between the main growth FG and the embedding of flowability are shown in Table 1 below.
The result of the examination focusing on the VD condition will be described.

[0009]

[Table 1]

The experiment shows that S is most likely to show the substrate dependency.
i Thermal oxide film substrate was mainly used. For the evaluation of the grown film, attention was paid to water and organic components in the film, and a Fourier transform infrared spectrophotometer was used. After the ozone CVD film was grown and taken out, it was placed in a sample chamber of an infrared spectrophotometer and its absorption spectrum was measured. Separately from this, the etching rate by a solution obtained by diluting the HF solution to a concentration of 0.5% was also evaluated. The thickness of the growth film is measured by a stylus type step measuring device (Alpha-step200, T
Encor) and ellipsometry (Ellipsometer L115
A, manufactured by Gertner) and the like. Also,
The embedding characteristics of the growth film are Hitachi's SEM (S-900)
Was evaluated.

Experimental results will be described below. First, the pressure dependence of the reaction gas will be described. Substrate temperature 4
The infrared absorption spectrum of the gas obtained by reacting TEOS with O ₃ at 00 ° C. is shown in FIG. The measurement was performed 20 times with a resolution of 4 cm ⁻¹ . The distance between the gas supply head and the Si substrate is 2
0 mm, and the optical axis of infrared rays was 4 mm on the substrate. The spread width of the infrared light is about 4 to 5 mm on each side of the optical axis.

With the introduction of TEOS and O ₃ , H ₂ O, OH groups, CO, CO ₂ and C═O bond were detected during the reaction. The intensity of CO ₂ is high at 101.3 kPa (normal pressure), while all the peaks are small at 6.7 kPa at low pressure, but a remarkable decrease in the CO ₂ peak is particularly noticeable.

In order to know the change of each component in the reaction gas when the pressure is different, FIG. 3 shows the pressure dependence of the absorber which is normalized to 93.3 kPa (700 Torr). The conversion method is shown in the figure as an absorption standardized by multiplying the absorption measured at 13.3 kPa by 93.3 / 13.3. When the pressure increases from low pressure to atmospheric pressure, the reaction proceeds, TEOS and O ₃ decrease, and CO ₂ increases. In the low pressure region, the rate of increase of CO _{2 with} the increase of pressure is large, but 70 kP
In the high pressure region of a or higher, there is a tendency for saturation. Considering the variation, the C = O bond is almost constant even when the pressure changes, and the ratio of CO _{2 to} the C = O bond is smaller as the pressure is lower. It was found that under the conventional AP-CVD conditions and in the vicinity thereof, the proportion of CO _{2 in} the reaction gas is high, but there are conditions under which the proportion of CO ₂ is low at low pressure.

Next, the pressure dependence of the surface shape of the grown film will be described. FIG. 4 shows the pressure dependence of the film surface morphology grown on a 300 nm Si thermal oxide film for 5 minutes. If the pressure is high, the surface will be highly uneven, and 93.3 kP
Voids were also found in the film grown under a pressure of a or higher.
As the pressure decreases, the surface irregularities become smaller, 13.3k
Below Pa, the surface became flat. In the previous section, it was stated that the ratio of CO _{2 to} the C═O bond in the reaction gas decreases when the pressure decreases, but the surface of the film grown in this low-pressure region has very small irregularities and the underlying dependence disappears. It was confirmed to do.

Next, the initial growth pressure and time dependence of the surface shape will be described. The dependence of initial growth conditions on the pressure modulation type CVD that combines low pressure growth and high pressure growth will be described. FIG. 5 shows the initial growth pressure dependence of the surface film morphology of the grown film obtained by successively performing low pressure initial growth and high pressure main growth. Initial growth time is 60 sec, high pressure main growth time is 3
It was set to 00 sec. As the initial growth pressure decreased, surface irregularities decreased, and at 10.0 kPa or less, a smooth surface was obtained.

Next, FIG. 6 shows the initial low pressure growth time dependence of the surface morphology after similar growth. The low pressure initial growth rate under these conditions was 80 nm / min. The 0 sec in FIG. 6 is the case where there is no initial low-pressure growth, which is a film directly grown on the Si thermal oxide film, and shows that the surface has severe irregularities. When the initial low-pressure film was grown for 15 seconds, surface irregularities became small, but voids existed in the film. 30se
It was found that the surface becomes flat and the underlayer dependence can be eliminated by the growth above c.

Next, the dependence of the flow characteristics of the grown film on the main growth pressure will be described. FIG. 7 shows an angle showing the shape of the Si thermal oxide film on the step when the initial low-pressure growth is performed at 6.7 kPa for 60 seconds and the high-pressure main growth is continuously performed for 5 minutes by changing the pressure. When the growth was performed directly on the step of the Si thermal oxide film without performing the growth of the low pressure specification, the stepped portion had a shape with a large unevenness. When the initial low-pressure growth was performed, when the high-pressure main growth pressure was 40 kPa, the step covering shape became almost conformal (isotropic). At higher pressures of 66.7 kPa or higher, the angle was remarkably decreased and flow characteristics were observed.

Next, Table 2 shows the filling characteristics of the Si thermal oxide film in the groove. When the low pressure specification was not grown, a large space was created at the bottom of the groove due to insufficient embedding. When initial low-pressure growth was performed at 6.7 kPa for 60 seconds, slit-like voids were observed in the middle of the groove at high-pressure main growth pressures of 40.0 kPa and 66.7 kPa, but 93.3
Complete embedding was performed for pressures of kPa and above.

[0019]

[Table 2]

As shown in FIG. 7, the flowability is 66.7.
Although it was remarkably recognized at kPa or higher, it was found from the result of the embedding property that a high pressure condition near atmospheric pressure is suitable.

Next, Table 3 shows the results of comparing the filling characteristics of narrow trenches of three types of polycrystalline Si having different CVD systems. LP-CVD is a low-pressure CVD of only 6.7 kPa, and CP-CVD is our proposal of pressure combination type CVD, AP-CVD (Atomic Pressur
e-CVD) is a so-called atmospheric pressure CVD of 101.3 kPa. In LP-CVD, slit-shaped voids were generated in all four types of grooves. In CP-CVD, slit-like voids were generated only in the narrowest groove. On the other hand, AP-
In CVD, slit-like voids were generated in three grooves from the narrow side, and complete filling was only in the widest groove. The pressure-combined CVD has the best filling characteristics,
Subsequently, it was confirmed that AP-CVD and finally low-pressure CVD are in sequence.

[0022]

[Table 3]

FIG. 8 is an enlarged view of the embedding cross section in order to explain the embedding characteristics of the pressure combination type CVD in more detail. Here, the groove of the underlying polycrystalline Si has a forward taper shape of 5 degrees on one side, but as shown in FIG. 8, the width of the opening is 0.20 μm, the depth is 0.62 μm, and the aspect ratio is 3. It was 1. It shows that there was no void and complete embedding was realized. This result is AP-
It surpasses CVD and is the current top data at the 0.20 μm level.

Next, the results of the reaction pressure dependence of the film quality will be shown. FIG. 9 is a typical infrared absorption spectrum of a film grown by changing the pressure. The film thickness was standardized based on each film thickness so that it would be the same as the film thickness grown at 93.3 kPa for 5 minutes. Absorption of OH group is observed in the vicinity of 930 cm ^-1 as shown in 3400 cm ^-1 and B shown by A in FIG. It was found that the lower the pressure, the greater the absorption of these, and the more the water content in the film increased. It was confirmed that the film formed by the CP-CVD method of the present invention has the same characteristics as the high quality film formed at 101.3 kPa.

Finally, FIG. 10 shows the growth pressure dependence of the etching rate for a 0.5% HF aqueous solution. Although there is variation, 20n on the high-voltage side with a boundary of around 30kPa
It was almost constant at m / min, but on the low pressure side, the etching rate increased as the pressure decreased and the film quality deteriorated.

Regarding the temperature dependence, the following results were obtained. Among the conditions of Table 1, the etching rate of the film grown on the Si substrate at a pressure of 101.3 kPa while changing the temperature is 250 ° C.,
81 at 300 ℃, 350 ℃, 400 ℃, and 450 ℃
nm / min, 64 nm / min, 41 nm / min, 20n
m / min and 18 nm / min.

Regarding the O ₃ concentration, the following results were obtained. Table 1
The infrared absorption spectrum of the grown film was measured while changing the O ₃ concentration in the range of 10 to 190 g / m ³ and the pressure at 101.3 kPa. It was confirmed that the absorption at 3400 cm ^-1 was at a low level at an O ₃ concentration of 65 g / m ³ or more, and g / m ³ or more, that is, in consideration of the experimental margin,
It was found that 4.0% or more is preferable. In other words, one oxygen atom is supplied from one molecule of ozone, and TE
A reaction formula in which carbon and hydrogen contained in OS are completely oxidized and converted into carbon dioxide and H ₂ O is conceivable. An ozone amount exceeding a value calculated based on this chemical formula, that is, TE
It was found that supplying 24 times the amount of ozone to the OS is effective for forming a high quality SiO ₂ film.

The etching rate of the film formed by the CP-CVD method of the present invention is shown by a black circle in FIG. 9 main growth
Although it was performed at 3.3 kPa, it was confirmed that the same characteristics as a film formed on a Si substrate at a high pressure in a region near the atmospheric pressure including a constant atmospheric pressure were obtained.

(Example 2) Next, the CVD-Si of the present invention
The multilayer wiring using the O ₂ film will be described. FIG.
An SiO ₂ film (P-T) having a film thickness of about 50 nm is formed by plasma CVD on the substrate on which the wiring 12 is formed on the insulating film 11.
EOS) 13 is formed, and then the SiO ₂ film 14 is formed by the pressure combination type CVD method (CP-CVD) described in the first embodiment.
3 is a cross section of a multi-layer wiring in which the wiring connection port is opened and the conductor 15 is embedded after the formation of the. Space for wiring 12 is 0.35
μm, but reflecting the characteristics of CP-CVD, SiO ₂
The embedding characteristics of the film 14 were good, and good insulation characteristics were obtained.

When the space between the wirings is reduced to 0.25 μm, the SiO ₂ film (P-TEOS) 23 formed by the conventional plasma CVD method as shown in the example of FIG. Therefore, when the coated glass 24 is formed, voids (voids) 25 that cannot be embedded are seen. On the other hand, when the SiO ₂ film 33 is formed by applying the CVD method of the present invention to the substrate in which the wiring 32 is formed on the insulating film 31 as shown in FIG. 13, a corner portion above the wiring 32 is formed. No overhang shape was observed, and even if the coating glass 34 was formed, it was possible to sufficiently fill the space between the wirings and flatten it. Note that FIG.
After forming the coated glass 44 as in the example shown in FIG.
Plasma CVD-Si with excellent film quality using iH ₄ as a material
It was also effective to stack the O ₂ film 45. C in this example
As the VD-SiO ₂ film 45, a plasma CVD film using SiH ₄ and N ₂ O was used.

Next, FIG. 15 shows an interlayer insulating film formed by CVD according to the present invention.
It is an example of forming only -SiO ₂ film. The pressure combination type C described in the first embodiment is applied to the substrate in which the wiring 52 mainly composed of tungsten (W) is formed on the insulating film 51.
The SiO ₂ film 53 was formed by the VD method. The formation conditions are a temperature of 400 ° C., a TEOS flow rate of 10 sccm, and an N ₂ flow rate of 5 sl.
The flow rate of O ₂ containing m and 7.5% of O ₃ was 5 slm, the initial growth process was 6.7 kPa for 60 seconds, and the main reaction was 101.3 kP.
a was set to 300 seconds. Next, after opening the wiring connection port, the cross section of the multilayer wiring in which the tungsten 54 of the conductor is embedded and then the upper aluminum wiring 55 is formed.

The 0.25 μm space between the wirings 52 could be filled with the SiO ₂ film 53 without voids. Further, as conditions for forming the SiO ₂ film 53, since TEOS is preceded by ozone and the pressure is set to a low pressure in the initial stage of growth, the surface of the wiring 52 mainly composed of W even at 400 ° C. Oxidation could be suppressed to a level where there was no practical problem, and good wiring characteristics were obtained.

When the SiO ₂ film 33 shown in FIG. 13, the SiO ₂ film 43 shown in FIG. 14, and the SiO ₂ film 53 shown in FIG. It can be tapered.

[0034]

According to the present invention, a high-quality Si oxide film can be embedded between wirings having a groove width of 0.20 μm and an aspect ratio of 3.1 without being affected by the underlying material and surface condition. Thus, it is possible to realize at low cost a semiconductor device having a fine multi-layer wiring with a minimum processing dimension of 0.3 μm or more, which has not been realized so far.

[Brief description of drawings]

FIG. 1 is an explanatory view of a pressure change in the film forming method of the present invention.

FIG. 2 is an infrared absorption spectrum diagram of a reaction gas at normal pressure and low pressure.

FIG. 3 is a characteristic diagram of pressure dependence of a reaction gas.

FIG. 4 is a characteristic diagram of pressure dependence of surface roughness.

FIG. 5 is a characteristic diagram of initial growth pressure dependency of surface roughness.

FIG. 6 is a characteristic diagram of initial low pressure growth time dependence of surface roughness.

FIG. 7 is a characteristic diagram showing the dependence of flow property on main growth pressure.

FIG. 8 is an explanatory view of a buried cross section according to the present invention.

FIG. 9 is an infrared absorption spectrum diagram of the grown film.

FIG. 10 is a characteristic diagram of pressure dependence of etching rate.

FIG. 11 is a cross-sectional view of a multilayer wiring structure showing an example of the present invention.

FIG. 12 is an explanatory diagram of a problem of a structure using a conventional CVD film.

FIG. 13 is a cross-sectional view of an interlayer insulating structure showing an example of the present invention.

FIG. 14 is a cross-sectional view of an interlayer insulating structure showing an example of the present invention.

FIG. 15 is a cross-sectional view of a multilayer wiring structure showing an example of the present invention.

[Explanation of symbols]

1 ... Si substrate, 2 ... P-TEOS film, 3 ... Polycrystalline Si
Films, 4 ... TEOS-O ₃ CVD SiO ₂ film, 11 ... Insulating film, 12 ... Lower layer wiring, 13 ... Lower layer insulating film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naruhiko Nakanishi 1-280 Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Nobuyoshi Kobayashi 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory of Manufacturing Co., Ltd. (72) Inventor Yutaka Kudo 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Nitrate Electronics Engineering Co., Ltd.

Claims (11)

[Claims] 1. A method for forming a silicon oxide film by reacting an organic compound of Si with ozone using oxygen gas containing 4% or more of ozone, wherein the film is initially formed at a low pressure, and then the pressure is applied. A method for forming a Si oxide film, which comprises forming the film at a higher pressure. 2. The method for forming a Si oxide film according to claim 1, wherein the initial low pressure growth and the subsequent high pressure growth are continuously performed. 3. The S according to claim 1, wherein the organic compound of Si is tetraethyl orthosilicate (TEOS).
Method of forming i oxide film. 4. A method of forming a silicon oxide film by reacting TEOS with ozone, which comprises 10 kPa in the initial stage of film formation.
A method for forming a Si oxide film, characterized in that the film is formed at a lower pressure than that, and then the film is formed at a pressure higher than 67 kPa. 5. The reaction formula according to claim 1, wherein one oxygen atom is supplied from one molecule of ozone to completely oxidize carbon and hydrogen contained in the organic compound of TEOSi to convert into carbon dioxide and H ₂ O. A method of forming a Si oxide film, which supplies an ozone amount exceeding a value calculated based on the above. 6. The substrate temperature according to claim 4, wherein the substrate temperature is 350.degree.
A method for forming a Si oxide film at 450 ° C. 7. The calculation according to claim 4, wherein one oxygen atom is supplied from one molecule of ozone to completely oxidize carbon and hydrogen contained in TEOS to convert into carbon dioxide and H ₂ O. Supply more ozone than
A method for forming a Si oxide film having a substrate temperature of 350 ° C to 450 ° C. 8. In a multilayer wiring of a semiconductor device, a first insulating film is formed on a substrate having a lower wiring formed thereon by a chemical vapor deposition method so as to cover the wiring, and the first insulating film is formed on the insulating film. A semiconductor device to which an interlayer insulating film having a silicon oxide film formed by the method described is applied. 9. In a multilayer wiring of a semiconductor device, a silicon oxide film is formed by the method according to claim 1 on a substrate having a lower layer wiring formed thereon, and a coated glass is coated on the silicon oxide film. A semiconductor device having a structure in which an interlayer insulating film is formed by stacking layers. 10. In a multilayer wiring of a semiconductor device, the wiring is coated on a substrate on which a lower wiring is formed.
A structure in which a silicon oxide film is formed by the method described above, coating glass is stacked on the silicon oxide film, and then a second insulating film is formed on the coating glass by a vapor phase chemical deposition method to form an interlayer insulating film. A semiconductor device characterized by: 11. In a multilayer wiring of a semiconductor device, the wiring is coated on a substrate on which a lower wiring is formed.
A semiconductor device having a structure in which a silicon oxide film is formed by the method described to form an interlayer insulating film.