JP3256708B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device,
In particular, it is used as a primary insulating film on a semiconductor substrate and a metal wiring, an interlayer insulating film between multilayer metal wirings, a final insulating film acting as a passivation film, a sidewall of a metal wiring, or a sidewall of a gate electrode of a field effect transistor. The present invention relates to a method for forming an insulating film by chemical vapor deposition using an organosilicon compound as a source gas.

[0002]

2. Description of the Related Art In recent years, high integration and high density of VLSI devices have rapidly progressed, and submicron processing has become essential for semiconductor processing technology. As the submicron processing progresses, the irregularities on the surface of the semiconductor substrate become more and more severe,
The aspect ratio has become large, and this unevenness has become a constraint in device manufacturing. What is most strongly desired to solve such a problem is a technique for flattening an interlayer insulating film formed between multilayer metal wirings.

Characteristics required for an interlayer insulating film for a submicron device include forming a space on the order of submicrons and achieving excellent step coverage for a pattern having a high aspect ratio of at least one. . As a method of forming an interlayer insulating film satisfying such a requirement, a chemical vapor deposition method (CVD method) using organosilane as a source gas is known. The CVD methods include plasma CVD, normal pressure CVD, reduced pressure CVD, pressure CVD,
A photo-excited CVD method and the like have been conventionally proposed.

Of these, an organic silane compound is used as a source gas, and an ozone gas is added as a reaction gas to the raw material gas to form a reaction gas at normal pressure.
An insulating film formed by a CVD method, that is, an atmospheric pressure ozone-organosilane CVD silicon oxide film is one of the most promising methods because of its particularly excellent flatness. A normal pressure CVD method using such a mixed gas of ozone and an organic silane compound as a source gas is disclosed in, for example, JP-A-61-776.
No. 95 and "Electrochemistry", 56, No. 7 (1988), pp. 527-532. As organic silane compounds, TEOS (tetraethoxysilane), OMCTS (octamethylcyclo
tetrasiloxane), HMDS (hexamethyldisiloxane), TMCTS
(tetramethylcyclotetrasiloxane), SOB (trimethylsily
l borate), DADBS (diacetoxydi-tertiary-butoxysilan
e), SOP (trimethylsilyl phosphate) and the like are known.

[0005] In addition, with the increase in integration and density of VLSI devices, the flatness of the insulating film used as the final protective film of the semiconductor device and the improvement of the film quality which affects the reliability of the device are strongly increasing. Has been requested. This is mainly to prevent intrusion of moisture or the like from the side wall of the final wiring.

[0006]

However, in a conventional method of manufacturing a semiconductor device in which an insulating film is formed by a CVD method using an organic silane-based compound as a source gas, the film formation rate and the film quality are largely dependent on the underlayer. There is a drawback that step coverage deteriorates and voids occur. For example, when an interlayer insulating film is formed, the film forming speed on the base insulating film is slow, the film forming speed on the aluminum wiring is fast, and there is little wraparound between the wirings, so that the space between the wirings is not filled. There is a disadvantage that a large void is formed between the aluminum wirings as a result of the upper portion being closed. As described above, the fact that a CVD film using an organic silane compound as a source gas has a large underlayer dependency is described in, for example, JP-A-61-77695 and "IEEE A" published in 1991, vol. 7
No. 652-658. When the voids are formed in this manner, cracks occur in the interlayer insulating film, the leakage current between the wirings increases, and the space between the wirings changes due to stress, which adversely affects the device characteristics.

In order to alleviate the drawbacks of the conventional semiconductor device manufacturing method, it has been proposed that the insulating film has a multilayer structure. For example, a thin oxide film (typically 3,000 mm or less) is formed on the surface of a base using TEOS and O ₂ as raw materials by plasma CVD to reduce the dependency on the base, and then excellent in flatness by ozone-TEOS normal pressure CVD. NSG (non-d
It has been proposed to form an oped silicate glass) film. However, even with this method, in a submicron device, the space between the wirings is extremely narrow, and furthermore, there is a disadvantage that a wiring step having a large aspect ratio of 1 or more cannot be embedded. Furthermore, it has been proposed to embed wiring steps using SOG (Spin On Glass).
The use of GaN has the disadvantage that gas (H ₂ O, etc.) does not escape from the lower part between the wirings, which adversely affects the reliability of the semiconductor device.

An object of the present invention is to solve the above-mentioned drawbacks of the conventional method of forming an insulating film, to provide excellent step coverage and flatness, and to be particularly effective and effective for use as an insulating film of a submicron device. Has film quality,
An object of the present invention is to provide a method capable of forming an insulating film without generation of cracks and voids, and thus capable of manufacturing a highly reliable semiconductor device.

[0009]

According to a method of manufacturing a semiconductor device according to the present invention, when an insulating film of a semiconductor device is formed by chemical vapor deposition using an organic silane and an oxidizing gas, first, a first process by plasma CVD is performed. A film is formed, a second film is formed by thermal CVD, and a reaction by an oxidizing gas is suppressed at an early stage of the second film. Further, in the method for manufacturing a semiconductor device according to the present invention, when an insulating film of a semiconductor device is formed by chemical vapor deposition using an organic silane and an oxidizing gas, a reaction with the oxidizing gas is performed at an initial stage or during the film formation.
It is characterized in that the temperature of the semiconductor substrate is suppressed by lowering it to a temperature at which thermal decomposition of the oxidizing gas is suppressed.

In a preferred embodiment of the present invention, the suppression of the reaction by the oxidizing gas can be performed by lowering the concentration of the oxidizing gas. The reduction in the concentration of the oxidizing gas can be performed by reducing the flow rate of the oxidizing gas supplied to the reaction chamber or by supplying a reducing gas capable of reacting with the oxidizing gas to the reaction chamber. .

In the present invention, for example, the following can be used as the organic silane. Tetraalkoxysilane (orthosilicate): Tetramethoxysilane (TEOS), tetraethoxysilane (TEO
S), tetra-n-propoxysilane, tetra-isopropoxysilane, tetra-n-butoxysilane Alkylalkoxysilane: methyltrimethoxysilane, methyltriethoxysilane, methyl-n-propoxysilane, methylisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane , Ethyltri-n-propoxysilane, ethyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane,
Phenyltrimethoxysilane dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldi-n-propoxysilane, diethyldiisopropoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane methyldimethoxysilane, methyldiethoxy Silane Dimethyl vinyl methoxy silane, dimethyl vinyl ethoxy silane Polysiloxane: tetrakis (dimethylsiloxy) silane Cyclosiloxane: octamethylcyclotetrasiloxane
(OMCTS), pentamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, trimethylcyclotrisiloxane disiloxane: hexamethyldisiloxane (HMDS), tetramethyldimethoxydisiloxane, dimethyltetramethoxydisiloxane, hexa Methoxydisiloxane alkylsilane: monomethylsilane, dimethylsilane,
Trimethylsilane, triethylsilane, tetramethylsilane, tetraethylsilane, allyltrimethylsilane,
Hexamethyldisilane Silylamine: dimethyltrimethylsilylamine, diethyltrimethylsilylamine Silane nitrogen derivative: aminopropyltriethoxysilane, trimethylsilyl azide, trimethylsilyl cyanide Silazane: hexamethyldisilazane, tetramethyldisilazane, octamethylcyclotetrasilazane, hexamethylcyclotri Silazane halogenated silanes and derivatives: trimethylchlorosilane, triethylchlorosilane, tri-n-propylchlorosilane, methyldichlorosilane, dimethylchlorosilane,
Chloromethyldimethylchlorosilane, chloromethyltrimethylsilane, chloropropylmethyldichlorosilane,
Chloropropyltrimethoxysilane, dimethyldichlorosilane, diethyldichlorosilane, methylvinyldichlorosilane, methyltrichlorosilane, ethyltrichlorosilane, vinyltrichlorosilane, trifluoropropyltrichlorosilane, trifluoropropyltrimethoxysilane, trimethylsilyl iodide Silanes include tris (trimethylsiloxy) borane (SOB), tris (trimethylsiloxy) phosphoryl (SOP), diacetoxy-tert-butoxysilane (DAD)
BS) can also be used. In the present invention, the above-mentioned organic silanes can be used alone or as a mixture of two or more organic silanes. In the case of using a mixture, the mixing ratio may be appropriately determined. As the chemical vapor deposition method, a normal pressure thermal CVD method, a low pressure thermal CVD method, a plasma CVD method, a photo CVD method, an ozone CVD method, or the like can be used.As the oxidizing gas, oxygen gas and ozone gas are used. .
Oxygen gas or ozone gas containing 1 to 7% by weight can be used.

[0012]

According to the method of manufacturing a semiconductor device according to the present invention, when an insulating film is formed by chemical vapor deposition using an organic silane and an oxidizing gas, a reaction with the oxidizing gas is performed at an initial stage or during the film formation. In this way, a large amount of ethanol, methanol, etc. are produced as intermediate reaction products, and the surface of the semiconductor wafer is ground-treated by these intermediate products. As a result, an insulating film having excellent film quality, which is excellent in embedding into a step and flatness, does not generate voids, and has a low moisture content, can be formed. It is not clear yet why the suppression of the reaction by the oxidizing gas results in the formation of an insulating film with good filling quality between steps and good film quality, but good results can be obtained. Has been confirmed experimentally.

The mechanism of forming an insulating film by chemical vapor deposition by the reaction between an organic silane and an oxidizing gas will be discussed below. Here, for convenience of explanation, TEOS is used as the organic silane, and oxygen containing about 5% by weight of ozone is used as the oxidizing gas. Ozone supplied to the reaction chamber is

As shown by O ₃ → O + O ₂ , it is decomposed into reactive oxygen and oxygen gas.
The reactive oxygen thus generated reacts with TEOS as follows. In this process, silicon oxide is generated on the base surface and is formed on the semiconductor wafer as an insulating film.

Embedded image That is, TEOS reacts with reactive oxygen to produce alcohols such as ethanol and methanol, aldehydes such as acetaldehyde and formaldehyde, and carboxylic acids such as acetic acid and formic acid as intermediate products, and finally carbon monoxide, It becomes carbon dioxide and water. In ordinary vapor phase growth, a sufficient amount of reactive oxygen is generated to efficiently form a silicon oxide film, and thus the above-mentioned intermediate product has a short lifetime. In the present invention,
As described above, at the beginning or during the film formation, the life of the above-mentioned intermediate product is prolonged by reducing the amount of reactive oxygen, so that a large amount of the intermediate product acts on the base surface of the semiconductor wafer. This reduces the background dependency. Among these intermediates, it is expected that alcohols such as ethanol and methanol, which are formed first, are effective in reducing the dependence on the substrate, but other intermediates are also effective. There is a possibility.

[0014]

(Embodiment 1) A silicon substrate as shown in FIG.
A BPSG film 12 having a thickness of 6000 mm is formed on 11 and an aluminum wiring 13 having a height of 1 μm is formed thereon with a line width of 0.5 μm and a space width of 0.5 μm. A plasma-TEOS CVD NSG film 14 was formed to a thickness of 3000 mm. The film forming conditions for the plasma-TEOS CVD NSG film 14 are as follows: a film forming temperature of 350 ° C., a film forming pressure of 2.2 Torr, TEOS supplied at a rate of 1.8 ml / min, and oxygen gas of 4.0 ml / min.
Per minute, and the RF power is 400KHz, 500W and 1
A total of 1 kW of 3.56 MHz and 500 W was used, and the deposition time was 20 seconds. The thickness of the plasma-TEOS CVDNSG film 14 is 3000 Å on the aluminum wiring 13, but only about 1000 形成 is formed on the side wall thereof.

Next, the silicon wafer was carried into a reaction chamber for performing chemical vapor deposition, and an ozone-TEOS CVD NSG film 15 was formed to a thickness of 10,000 で under the following film forming conditions. That is, in this embodiment, ozone-TEOS C using TEOS as the organic silane and ozone as the oxidizing gas is used.
In forming an SiO ₂ film by VD, a reducing gas, ie, a gas obtained by diluting propylene (C ₃ H ₆ ) acting as an ozone killer to 2% with a nitrogen gas during the initial 60 seconds of the film formation. Is supplied at a flow rate of 7 liters / minute to suppress the reaction by the oxidizing gas. Other conditions are as follows, but in this specification, the gas flow rate indicates a flow rate in a standard state of 0 ° C. and 1 atm.

[Table 1] Deposition temperature 400 ℃ Deposition pressure Atmospheric pressure Deposition time 545 seconds Nitrogen gas flow to gas bubbler 1.5 l / min Temperature bath temperature 65 ℃ Oxygen flow to ozone generator 7.5 l / min Ozone concentration 5 wt% Carrier N ₂ gas flow rate 18 l / min The ozone-TEOS CVD NSG film 15 formed in this manner fills a narrow space between the aluminum wirings 13, has good step coverage, and has excellent flatness. It had good film quality with no voids formed.

Comparative Example 1 As a comparative example 1, as shown in FIG. 2, a BPSG film 12 is formed on a silicon substrate 11, an aluminum wiring 13 is further formed thereon, and a plasma is formed on the BPSG film and the aluminum wiring. -A TEOS CVD NSG film 14 was formed to a thickness of 3000 mm. Up to this point, the process is the same as that of the first embodiment, and the line width, space, and height of the aluminum wiring 13 are the same as those of the first embodiment.
Is the same as Thereafter, the substrate was placed in a reaction chamber, and an ozone-TEOS CVD NSG film 16 was formed to a thickness of 10,000 mm under the same film forming conditions as in Example 1 without using propylene as a reducing gas. In Comparative Example 1, the ozone-TEOS CVD NSG film was used.
The embedding between the 16 aluminum wirings 13 was defective, and many voids 17 were formed, which deteriorated the element characteristics.

(Embodiment 2) Also in this embodiment, an aluminum wiring is formed on a silicon substrate, a plasma-TEOS CVD NSG film is formed thereon, and then a silicon wafer is loaded into a reaction chamber. Is the same as in the first embodiment. In this example, the heating temperature of the silicon wafer, the temperature to suppress the thermal decomposition of ozone, for example,
The temperature was initially set at 350 ° C., and the temperature was raised to 400 ° C. within 3 seconds 50 seconds after the start of film formation. Other conditions were the same as in Example 1.
And 2. As described above, by lowering the temperature of the silicon wafer in the initial stage of film formation, thermal decomposition of ozone is suppressed, and as a result, generation of reactive oxygen is suppressed, and the base treatment is performed as described above,
It is possible to form an ozone-TEOS CVD NSG film having excellent burying property and flatness and excellent film quality without voids. As in this embodiment, it is difficult to raise the temperature of the silicon wafer rapidly by ordinary resistance heating. Therefore, in this embodiment, a lamp heating method is used.

(Embodiment 3) In this embodiment, plasma TEOS CVD NSG is performed in the same manner as in the previous embodiment.
The steps up to the step of forming the film on the aluminum wiring and then carrying it into the reaction chamber are the same as in the previous example. In the above-described embodiment, the concentration of ozone is always 5% by weight with respect to the supplied oxygen. However, in this example, the concentration is reduced to 2% by weight for 50 seconds after the start of film formation, and thereafter, for about 10 seconds. It was increased to 5% by weight. In this way, the amount of reactive oxygen generated can be reduced by lowering the ozone concentration at the initial stage of film formation, and as a result, a large amount of reaction intermediate products are generated, thereby reducing the surface of the silicon wafer. Ozone-T with excellent film quality with good embedding in steps, excellent flatness and no generation of voids
EOS CVD NSG film can be formed.

The present invention is not limited to the above-described embodiment, but can be variously modified and modified. The organic silane is not limited to only TEOS described above, and various organic silanes can be used as described above. Further, the oxidizing gas is not limited to the above-mentioned ozone, and for example, hydrogen peroxide can be used. Further, in the above-described embodiment, the plasma-TEOS CVD NSG film is formed on the aluminum wiring, and the ozone-TEOS CVD NSG film is formed thereon. May be formed, or the plasma-TEOS CVD NSG film may be omitted. Further, in the above-described embodiment, the interlayer insulating film is formed, but a first layer insulating film or a final insulating film may be formed.

[0020]

As described above, according to the method of manufacturing a semiconductor device according to the present invention, when an insulating film is formed on the surface of a semiconductor wafer by chemical vapor deposition using organosilane, the dependence of the insulating film on the underlayer is reduced. It is possible to form an insulating film having excellent film quality, which is excellent in embedding into a step and flatness, has no voids, and has a low moisture content. Therefore, the reliability of the semiconductor device formed as described above can be improved. Further, in practicing the present invention, a simple process of suppressing the reaction due to the oxidizing gas only needs to be added to the conventional vapor phase growth process, so that the manufacturing process is simplified and the throughput is improved. Become.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor device formed by one embodiment of a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing a semiconductor device formed by a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

 11 Silicon substrate 12 BPSG film 13 Aluminum wiring 14 Plasma-TEOS CVD NSG film 15 Ozone-TEOS CVD NSG film

Continuation of the front page (56) References JP-A-4-56323 (JP, A) JP-A-3-123029 (JP, A) JP-A-3-198340 (JP, A) JP-A-61-77695 (JP, A) , A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/316

Claims (5)

(57) [Claims] In forming an insulating film of a semiconductor device by chemical vapor deposition using an organic silane and an oxidizing gas, first, a first film is formed by plasma CVD, and then a second film is formed by thermal CVD. A method for manufacturing a semiconductor device, comprising forming a film and suppressing a reaction due to an oxidizing gas at an early stage of the second film formation. 2. The method for manufacturing a semiconductor device according to claim 1, wherein ozone is used as an oxidizing gas for the CVD for the second film formation. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the suppression of the reaction by the oxidizing gas in the second film formation is performed by supplying a reducing gas to a reaction chamber. . 4. When forming an insulating film of a semiconductor device by chemical vapor deposition using an organic silane and an oxidizing gas, a reaction with an oxidizing gas is performed at an initial stage or in the course of film formation, and the temperature of the semiconductor substrate is controlled by the oxidation. A method for manufacturing a semiconductor device, wherein the temperature is suppressed by lowering to a temperature at which thermal decomposition of a reactive gas is suppressed. 5. The method according to claim 4, wherein ozone is used as the oxidizing gas.