JPH06283509A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form an insulating film, which is good in step coverage and flatness and at the same time, is good also in film quality, when the insulating film of a semiconductor device is formed by a chemical vapor deposition method using organic silane gas as raw gas. CONSTITUTION:When aluminum wirings 13 are formed on an insulating film 12 on a semiconductor substrate 11, a plasma TEOSCVD film 14 is formed thereon and thereafter, the substrate 11 is put in a reaction chamber and an insulating film is formed by a reaction using TEOS gas and ozone gas, a large quantity of an intermediate reaction product, such as an ethanol and a methanol, is produced by inhibiting the generation of oxidizing oxygen in the film-forming initial stage. Thereby, a surface treatment is performed and the ozone- TEOSCVDNSG film 15, which is improved its step coverage and flatness and at the same time, is inhibited also the generation of voids, can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of 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 multi-layer 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 that can be formed 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 been rapidly advanced, and submicron processing has become essential in semiconductor processing technology. As the submicron processing progresses, the unevenness of the semiconductor substrate surface becomes more and more intense,
The aspect ratio becomes large, and this unevenness becomes a constraint in device manufacturing. What is most strongly desired for solving such a problem is a technique for flattening an interlayer insulating film formed between multi-layer metal wirings.

Characteristics required for an interlayer insulating film for submicron devices include forming a space on the order of submicron and realizing excellent step coverage for a pattern having a high aspect ratio of 1 or more. . A chemical vapor deposition method (CVD method) using organic silane as a raw material gas is known as a method of forming an interlayer insulating film that satisfies such requirements. As the CVD method, plasma CVD, atmospheric pressure CVD method, low pressure CVD method, pressure CVD method,
The photo-excited CVD method has been proposed in the past.

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

Further, in the insulating film used as the final protective film of the semiconductor device, the flatness and the film quality which influences the reliability of the element are strongly improved due to the higher integration and higher density of the VLSI device. Is required. This is mainly to prevent intrusion of moisture or the like from the side wall of the final wiring.

[0006]

However, in the conventional method for manufacturing a semiconductor device in which an insulating film is formed by a CVD method using an organosilane compound as a raw material gas, the film formation rate and the film quality are largely dependent on the underlying layer. There is a drawback that the step coverage becomes worse and a void is generated. For example, when forming an interlayer insulating film, the film forming speed on the underlying insulating film is slow, the film forming speed on the aluminum wiring is fast, and the wraparound between the wirings is small, so that the space between the wirings is not filled. As a result of the upper part being blocked, a large void is formed between aluminum wirings. Thus, the fact that a CVD film using an organic silane-based compound as a raw material gas has a large dependency on the underlayer is described in, for example, Japanese Patent Laid-Open No. 61-77695 and "The Institute of Electrical Engineers of Japan", Volume 111. 7
Issue, pages 652-658. When the voids are formed in this way, cracks occur in the interlayer insulating film, the leak current between the wirings increases, and the space between the wirings changes due to stress, which adversely affects the element characteristics.

In order to alleviate the above-mentioned drawbacks of the conventional semiconductor device manufacturing method, it has been proposed that the insulating film has a multilayer structure. For example, in order to alleviate the dependency on the substrate, a thin oxide film (usually 3000 Å or less) is formed on the surface of the substrate by plasma CVD using TEOS and O ₂ as raw materials, and then ozone-TEOS atmospheric pressure CVD is used to achieve excellent flatness. NSG (non-d
It has been proposed to form an oped silicate glass) film. However, even with this method, the space between wirings is extremely narrow in a submicron device, and further, a wiring step having a large aspect ratio of 1 or more cannot be embedded. Furthermore, it is also proposed to fill the wiring step using SOG (Spin On Glass), but SOG
When used, the gas (H ₂ O, etc.) from the lower portion between the wirings does not escape, and there is a drawback that the reliability of the semiconductor device is adversely affected.

The object of the present invention is to solve the above-mentioned drawbacks of the conventional insulating film forming method and to have excellent step coverage and flatness, and in particular, it is effective as an insulating film for submicron devices and excellent. It has a film quality,
An object of the present invention is to provide a method capable of forming an insulating film without generation of cracks or voids, and thus manufacturing a highly reliable semiconductor device.

[0009]

According to the method of manufacturing a semiconductor device of the present invention, when the insulating film of the semiconductor device is formed by chemical vapor deposition using organic silane and an oxidizing gas, oxidation is performed at the initial stage or during the film formation. It is characterized in that it suppresses the reaction caused by the volatile gas.

In a preferred embodiment of the present invention, the suppression of the reaction by the oxidizing gas can be carried out by lowering the concentration of the oxidizing gas. The concentration of the oxidizing gas can be reduced by reducing the flow rate of the oxidizing gas supplied to the reaction chamber or supplying a reducing gas capable of reacting with the oxidizing gas to the reaction chamber. . Further, the reduction of the reaction due to the oxidizing gas can be carried out by lowering the temperature of the semiconductor substrate to a temperature at which the thermal decomposition of the oxidizing gas is suppressed.

In the present invention, the following organic silanes can be used, for example. Tetraalkoxysilane (orthosilicate ester): Tetramethoxysilane (TEOS), Tetraethoxysilane (TEO)
S), tetra-n-propoxysilane, tetra-iso-propoxysilane, 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 Dimethylvinylmethoxysilane, Dimethylvinylethoxysilane Polysiloxane: Tetrakis (dimethylsiloxy) silane Cyclosixane: 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, trimethylsilylazide, trimethylsilylcyanide silazane: hexamethyldisilazane, tetramethyldisilazane, octamethylcyclotetrasilazane, hexamethylcyclotriazane Silazane halogenated silanes and derivatives: trimethylchlorosilane, triethylchlorosilane, tri-n-propylchlorosilane, methyldichlorosilane, dimethylchlorosilane,
Chloromethyldimethylchlorosilane, chloromethyltrimethylsilane, chloropropylmethyldichlorosilane,
Chloropropyltrimethoxysilane, dimethyldichlorosilane, diethyldichlorosilane, methylvinyldichlorosilane, methyltrichlorosilane, ethyltrichlorosilane, vinyltrichlorosilane, trifluoropropyltrichlorosilane, trifluoropropyltrimethoxysilane, trimethylsilyliodide In addition, organic As silanes, 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 may be used alone, or two or more organic silanes may be mixed and used. When mixed and used, the mixing ratio may be set appropriately. Further, as the vapor phase chemical growth method, an atmospheric pressure thermal CVD method, a reduced pressure thermal CVD method, a plasma CVD method, an optical CVD method, an ozone CVD method, or the like can be used, and as the oxidizing gas, oxygen gas or ozone gas can be used. .
Oxygen gas, ozone gas, etc. containing 1 to 7 wt% 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 by the oxidizing gas occurs at the initial stage or during the film formation. By suppressing this, a large amount of ethanol, methanol, etc. are generated as intermediate reaction products, and the surface of the semiconductor wafer is subjected to undercoating by this intermediate product, so the underlayer dependence of the insulating film is relaxed. Thus, it is possible to form an insulating film having an excellent film quality that is excellent in burying property in a step and flatness, does not generate a void, and has a low water content. Although the reason why an insulating film with good film quality and good embedding between steps can be formed by suppressing the reaction due to the oxidizing gas in this way has not been clarified, but good results can be obtained. Has been confirmed experimentally.

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

## STR1 ## As shown in 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 surface of the base and is deposited as an insulating film on the semiconductor wafer.

[Chemical 2] 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 normal vapor phase growth, sufficient reactive oxygen is generated to efficiently form a silicon oxide film, and therefore the above-mentioned intermediate product has a short life. In the present invention,
As described above, the life of the above-mentioned intermediate product is lengthened by decreasing the amount of reactive oxygen during the initial stage or in the middle of the film formation so that a large amount of the intermediate product acts on the underlying surface of the semiconductor wafer. It is to reduce the background dependency. Among these intermediate products, it is expected that alcohols such as ethanol and methanol which are initially formed are effective in reducing the dependency on the substrate, but other intermediate products are also effective. There is a possibility that

[0014]

EXAMPLES Example 1 Silicon substrate as shown in FIG.
A BPSG film 12 with a thickness of 6000Å is formed on 11 and an aluminum wiring 13 with a height of 1 μm is formed on it with a line width of 0.5 μm and a space width of 0.5 μm, and on this BPSG film and aluminum wiring. A plasma-TEOS CVD NSG film 14 was formed to a thickness of 3000Å. As conditions for forming the plasma-TEOS CVD NSG film 14, the film forming temperature was 350 ° C., the film forming pressure was 2.2 Torr, TEOS was supplied at a rate of 1.8 ml / min, and oxygen gas was 4.0 ml / min.
The RF power is 400KHz, 500W and 1
A total of 1 kW of 3.56 MHz and 500 W was used, and the film formation time was 20 seconds. The thickness of the plasma-TEOS CVD NSG film 14 is 3000 Å on the aluminum wiring 13, but only about 1000 Å is formed on the side wall thereof.

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

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

Comparative Example 1 As 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 plasma is formed on the BPSG film and the aluminum wiring. -TEOS CVD NSG film 14 was formed to a thickness of 3000 Å. The process up to this point is the same as in the first embodiment described above, and the line width, space, and height of the aluminum wiring 13 are also the same as in the first embodiment.
Is the same as. Then, it was placed in a reaction chamber and an ozone-TEOS CVD NSG film 16 was formed to a thickness of 10000 Å under the same film forming conditions as in Example 1 without using propylene as a reducing gas. In Comparative Example 1, ozone-TEOS CVD NSG film
The embedding between the 16 aluminum wirings 13 was defective and many voids 17 were formed, which deteriorated the device characteristics.

(Embodiment 2) Also in this embodiment, until aluminum wiring is formed on a silicon substrate, a plasma-TEOS CVD NSG film is further formed thereon, and then a silicon wafer is carried into a reaction chamber. Is the same as in the first embodiment described above. In this example, the heating temperature of the silicon wafer is set to a temperature that suppresses thermal decomposition of ozone, for example,
The temperature was initially set to 350 ° C., and 50 seconds after the start of film formation, the temperature was raised to 400 ° C. within 3 seconds. Other conditions are Example 1
And the same as 2. Thus, the thermal decomposition of ozone is suppressed by lowering the temperature of the silicon wafer in the initial stage of film formation, and as a result, the 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 with excellent film quality that is excellent in embedding property and flatness and has no void. Since it is difficult to raise the temperature of the silicon wafer abruptly by ordinary resistance heating as in this example, the lamp heating method was used in this example.

(Embodiment 3) Also in this embodiment, the steps up to the step of forming the plasma TEOS CVD NSG film on the aluminum wiring and then carrying it into the reaction chamber are the same as in the previous example. In the embodiment described above, the concentration of ozone is set to be always 5% by weight with respect to the supply oxygen, but in this example, it is reduced to 2% by weight for 50 seconds after the start of film formation, and then about 5% by weight.
It was increased to 5% by weight in 10 seconds. In this way, the ozone concentration at the early stage of film formation can be lowered to reduce the amount of reactive oxygen generated, and as a result, a large amount of reaction intermediate products are generated, which causes the surface of the silicon wafer to be generated. Can be used to form an ozone-TEOS CVD NSG film of excellent film quality, which has good burying properties in steps, excellent flatness and no voids.

The present invention is not limited to the above-mentioned embodiments, but various modifications and variations are possible. The organic silane is not limited to the TEOS described above, and various organic silanes can be used as described above. Further, the oxidizing gas is not limited to ozone described above, and hydrogen peroxide, for example, may 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. However, instead of the plasma-TEOS CVD NSG film, another film is formed. The insulating film may be formed, or the plasma-TEOS CVD NSG film may be omitted. Further, although the interlayer insulating film is formed in the above-described embodiments, the first layer insulating film and the final insulating film can be formed.

[0020]

As described above, according to the method for manufacturing a semiconductor device of the present invention, when forming an insulating film on the surface of a semiconductor wafer by chemical vapor deposition using organic silane, the underlying dependency of the insulating film is It is possible to form an insulating film having an excellent film quality, which can be reduced, and which is excellent in the filling property in the step and the flatness, does not generate a void, and has a small water content. Therefore, the reliability of the semiconductor device thus formed can be improved. Further, in carrying out the present invention, it suffices to add a simple process of suppressing the reaction due to the oxidizing gas to the conventional vapor phase growth process, which simplifies the manufacturing process and improves the throughput. Become.

[Brief description of drawings]

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

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

[Explanation of symbols]

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

Claims (5)

[Claims] 1. When forming an insulating film of a semiconductor device by chemical vapor deposition using organic silane and an oxidizing gas, the reaction by the oxidizing gas is suppressed at the initial stage or during the film formation. Manufacturing method. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the suppression of the reaction by the oxidizing gas is carried out by reducing the concentration of the oxidizing gas. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the concentration of the oxidizing gas is reduced by reducing the flow rate of the oxidizing gas supplied to the reaction chamber. 4. The method of manufacturing a semiconductor device according to claim 2, wherein the concentration of the oxidizing gas is reduced by supplying a reducing gas to the reaction chamber. 5. The semiconductor device according to claim 1, wherein the reaction due to the oxidizing gas is reduced by lowering the temperature of the semiconductor substrate to a temperature at which thermal decomposition of the oxidizing gas is suppressed. Manufacturing method.