JP2666681B2 - 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, and more particularly to a method for forming an interlayer insulating film.

[0002]

2. Description of the Related Art With the recent increase in the degree of integration and speed of semiconductor devices, metal film wirings have become multi-layered, and the metal film wirings themselves tend to be finer and have a higher aspect ratio. In manufacturing such a semiconductor device, it is important to form an interlayer insulating film between metal film wirings having different layers with sufficient smoothness.

As a method of forming an interlayer insulating film having a smooth surface, for example, 1991 VMIC Conference (VLSL Multilevel Intercon) is used.
Connection Conference) Proceedings, No. 4
Are described in page 35, second page 441, there is a method of forming a silicon oxide based glass layer in a plasma atmosphere using tetraethoxysilane _{(Si (O 2 H 5)} 4) water vapor (H ₂ O) . Hereinafter, this prior art will be described with reference to the drawings. FIG. 2 is a schematic view of a silicon oxide-based glass film forming apparatus used in the prior art and the present invention. Tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ or TEOS) and steam (H ₂ O) are introduced into the reaction chamber 1 through the gas pipe 2 and the upper electrode 3. Base substrate 4 (wafer)
Is held on a temperature-controlled heater 5 and is grounded. A high frequency power supply 6 having an oscillation frequency of 13.56 MHz is connected to the upper electrode 3, and can be turned on / off periodically as required, like a rectangular wave. The ratio of the ON time to the entire time is called a duty ratio.
The repetition frequency of on / off uses, for example, 100 KHz. After the reaction between the tetraethoxysilane and the steam, the exhaust holes 8
Is more exhausted. Next, FIG. 7 shows a time chart of a gas flow rate and the like at the time of forming a silicon oxide-based glass film of the prior art.
Tetraethoxysilane 100 sccm, steam 50
It is introduced into the reaction chamber at a flow rate of sccm. Base substrate is 10
It is kept at 0 ° C. At the same time, power is supplied from the high frequency power supply 6 at a duty ratio of 30%, thereby forming a silicon oxide glass film having a smooth surface shape. When the conventional technique described above is applied to the formation of an interlayer insulating film of a semiconductor device, as shown in FIG. 8A, a silicon oxide film 22 on a silicon substrate 21 is selectively covered to form a metal film wiring 23. When the formed base substrate is prepared, and a silicon oxide-based glass film 24 is formed thereon as shown in FIG. 8B using the above-described conventional technique, a smooth surface is obtained.

[0004]

In forming a silicon oxide-based glass film according to the prior art, when high-frequency power is turned on, tetraethoxysilane and water vapor are reacted in a gas phase to obtain a silicon oxide having fluidity. A glass precursor is formed, and in the off state, the precursor reaches the underlying substrate, is fluidized, and further reacted by a heater heated to about 100 ° C. to form a silicon oxide-based glass film containing silicon dioxide as a main component. To form For this reason, the thermal energy for forming the silicon oxide-based glass film is lower than that at a temperature of 300 ° C. or higher used for forming an ordinary SOG film. Therefore, a silicon oxide-based glass film having low density is formed. Since the silicon oxide-based glass film having low density has a strong tensile stress, as shown in FIG.
Is generated. Such a crack causes a disconnection or a short circuit in a subsequent step of forming a metal film wiring in an upper layer, which causes a problem of lowering the yield of the semiconductor device. Further, in the via hole, disconnection is caused by water vapor released from the silicon oxide-based glass film having low density.

That is, when forming an upper metal film wiring after forming an interlayer insulating film, first, as shown in FIG.
As shown in (b), a via hole 26 is opened using the photoresist film 25 as a mask. Next, as shown in FIG. 9C, in the step of removing the photoresist film 26 and subsequently forming the upper metal film wiring 27 as shown in FIG. Since the silicon-based glass film 24 easily absorbs water vapor in the atmosphere and emits it by heating, the metal film does not adhere to via holes where water vapor is likely to stagnate due to heating during the formation of the metal film. A poisoned via hole 28 is generated. This poisoned via hole breaks the metal film wiring,
This causes serious problems such as remarkable reduction in the yield and reliability of the semiconductor device.

[0006]

The method of manufacturing a semiconductor device of the present invention, in order to solve the problems] includes the steps of coating a base substrate to form a silicon oxide glass film from a plasma atmosphere containing organic silane gas and water vapor or oxygen gas, fluorine and Steam or acid
And a step of densifying the silicon oxide type glass film in a plasma atmosphere of a gas containing hydrogen is repeatedly alternately includes the step of forming an interlayer insulating film.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

The silicon oxide glass forming apparatus used in the first embodiment of the present invention is the same as that used in the prior art, and is shown in FIG.

The flow rate of each gas of tetraethoxysilane, water vapor and carbon tetrafluoride is controlled, and is introduced into the reaction chamber 1 from the upper electrode 3 through the gas pipe 2. The base substrate 4 is set on a heater 5 and temperature-controlled. A high-frequency power supply having an oscillation frequency of 13.56 MHz is connected to the upper electrode 3, and can be turned on / off periodically as needed. FIG. 1 shows a time chart of a gas flow rate and the like when forming a silicon oxide-based glass film in the first embodiment of the present invention.

First, tetraethoxysilane 100 scc
m, water vapor 50 sccm, high frequency power 150 W, heating temperature 100 ° C., silicate glass film 5
0 nm is formed. At this time, the high frequency power is 100 kHz
By setting the duty ratio to 30% at a repetition frequency of ON / OFF, fluidity is generated and a silicon oxide-based glass film whose main component is silicon dioxide and has a smooth surface is formed.
Subsequently, the tetraethoxysilane gas is stopped and 10 sccm of the carbon tetrafluoride gas is introduced, and at the same time, the high frequency power is set to 400 W and the duty ratio is set to 100%. Carbon tetrafluoride generates fluorine radicals by plasma,
The present inventors have found that fluorine radicals have a catalytic action in a silicon oxide-based glass film to promote a polycondensation reaction between water and unreacted Si-OH bonds of tetraethoxysilane and water. Thus, the range in which the film quality is densified is about 50 nm from the surface. Furthermore, formation of silicon oxide glass film and film modification using fluorine radicals (densification treatment)
Is performed separately in time, the high-frequency power at the time of film modification can be increased, the kinetic energy of ions can be increased, and the film can be further densified. By repeating the above, a desired silicon oxide-based glass film is obtained.

Next, the formation of an interlayer insulating film of a semiconductor device will be described as a specific example of this embodiment.

First, as shown in FIG. 3A, a base substrate having a silicon substrate 21, on which a silicon oxide film 22, a device such as a transistor (not shown), and a metal film wiring 23 are formed, is prepared. On this, as shown in FIG. 3B, a silicon oxide-based glass film 24-1 having a smooth surface is formed to a thickness of 50 nm by using tetraethoxysilane and water vapor.
Subsequently, as shown in FIG. 3C, the silicon oxide-based glass film 24-1 is turned into a densified silicon oxide-based film 30-1 by exposure to fluorine radicals and ions 29 in the carbon tetrafluoride plasma. Become. Similarly, as shown in FIG. 4A, a silicon oxide-based glass film 24-2 is formed,
As shown in FIG. 4B, a densification process is performed. By repeating such formation and densification treatment of the silicon oxide-based glass film, for example, ten times, as shown in FIG.
The densified silicon oxide-based glass film 30 is formed as a 1 μm-thick interlayer insulating film. The silicon oxide-based glass film formed in the prior art has a sparse film quality such that the film thickness after heat treatment at 800 ° C. shrinks by 15% compared to the film thickness when formed. 5% according to one embodiment
Improved to shrinkage. As a result, cracks in the film and poisoned via holes, which are observed in the related art, are not generated.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a schematic view of a silicon oxide glass film forming apparatus used in the second embodiment of the present invention.

The difference from the first embodiment is that a high frequency power source 6 and a low frequency power source 7 can be alternately selected by a switch 9 as a power source for forming plasma. The formation of the silicon oxide-based glass film will be described with reference to FIG.

First, a high frequency of 13.56 MHz was applied to the silicon oxide glass film at a duty ratio of 3 in the same manner as in the first embodiment.
It is formed with 0% power and 150 W. Subsequently, the power supply was switched to a low frequency power supply of 400 kHz, and 400 W,
The film reforming process is performed for 20 seconds with a duty ratio of 60%. By using a low frequency, the kinetic energy of the ions is increased, the denseness of the film is further improved as compared with the first embodiment, and the film shrinkage after the heat treatment at 800 ° C. is improved to 3%. .

Although the above description has been made using tetraethoxysilane, the present invention can be applied to a case where a silicon oxide-based glass film is formed using other organic silanes such as alkoxylan and siloxane. Further, oxygen may be used instead of steam. Further, as the gas containing fluorine, other than carbon tetrafluoride gas, dicarbon hexafluoride gas (C2 F6) or fluorine gas (F2) may be used.

[0018]

As described above, the present invention provides a silicon oxide glass film formed from a plasma atmosphere containing an organic silane gas such as tetraethoxysilane and water vapor or oxygen gas by using the catalytic action of fluorine radicals. Since the interlayer insulating film of the semiconductor device is formed by densification, cracks in the interlayer insulating film and poisoned via holes at the time of forming upper layer wiring do not occur, and the yield and reliability of the semiconductor device are further improved. Having.

[Brief description of the drawings]

FIG. 1 is a time chart of a gas flow rate and the like in a first embodiment of the present invention.

FIG. 2 is a schematic view of a silicon oxide-based glass film forming apparatus used in the first embodiment of the present invention and the prior art.

FIGS. 3A to 3C are diagrams for explaining the first embodiment of the present invention.
It is a process order sectional view divided and shown to (c).

4 (a) to 4 (c) are cross-sectional views in the order of steps for explaining a step following the step corresponding to FIG. 3;

FIG. 5 is a schematic diagram of a silicon oxide-based glass film forming apparatus used in a second embodiment of the present invention.

FIG. 6 is a time chart of a gas flow rate and the like in a second embodiment of the present invention.

FIG. 7 is a time chart of a gas flow rate and the like in a conventional silicon oxide-based glass film formation.

8 (a) to 8 (c) are cross-sectional views in a process order for explaining a conventional technique.

FIGS. 9A to 9D are cross-sectional views in the order of steps for explaining generation of a poisoned via hole according to the conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Gas piping 3 Upper electrode 4 Base substrate 5 Heater 6 High frequency power supply 7 Low frequency power supply 8 Exhaust hole 9 Switch 21 Silicon substrate 22 Silicon oxide film 23 Metal film wiring 24, 24-1, 24-2 Silicon oxide glass Film 25 Photoresist film 26 Via hole 27 Upper metal film wiring 28 Poisoned via hole 29 Fluorine radicals and ions 30, 30-1, 30-2 Densified silicon oxide-based glass film

Claims (3)

(57) [Claims] 1. A a process for coating a base substrate to form a silicon oxide glass film from a plasma atmosphere containing organic silane gas and water vapor or oxygen gas, fluorine and steam addition
Forming an interlayer insulating film by alternately repeating the step of densifying the silicon oxide-based glass film in a plasma atmosphere of a gas containing oxygen . 2. The method according to claim 1, wherein the organic silane is tetraethoxysilane. 3. A method for generating a plasma containing oxygen gas.
Generates a plasma of fluorine-containing gas at a lower frequency
The method for manufacturing a semiconductor device according to claim 1.