JPH1174260A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device and its manufacture, wherein silicon group is condensed and dehydrated around the atmospheric pressure at a high degree, moisture absorption by an insulating thin film is prevented, so as to suppress the corrosion of a conductive layer and the deterioration of the functions of the insulating thin film, and the increase of the contact resistance between the lower layer wiring and the upper layer wiring in a multilayered interconnecting structure is prevented. SOLUTION: In a method of manufacturing a semiconductor device having an interconnecting structure composed of, at least one conductive layer on a semiconductor substrate 1 through an inter-layer insulating film 4, the inter- layer insulating film 4 is formed on the semiconductor substrate 1 by baking hydrogen silsesquioxane resin, and the inter-layer insulating film 4 is heat treated within a pressure range of 1 to 1000 Torr at a temperature of 150 to 550 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device having an insulating thin film and a method for manufacturing the semiconductor device.
More specifically, it enables the condensation and dehydration of silanol groups in the insulating thin film to be performed at a high degree near normal pressure, and prevents moisture absorption in the insulating thin film to suppress corrosion of the conductive layer and deterioration of the function of the insulating thin film. The present invention relates to a semiconductor device in which a contact resistance between a lower wiring and an upper wiring in a multilayer wiring structure is prevented from increasing, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with miniaturization of semiconductor elements, that is, high integration of semiconductor devices, a multilayer wiring structure has been adopted on a semiconductor substrate. As an insulating film of a semiconductor device having such a multilayer wiring structure, CVD is generally used.
A silicon oxide film formed by a method such as a spin coating method or the like is used.

In the case of manufacturing a semiconductor device having the above-described multilayer wiring structure, a lower wiring is formed on a semiconductor substrate via an insulating film, an interlayer insulating film is further formed, and the interlayer insulating film is selectively etched. Then, a via hole is provided on the lower layer wiring, and a metal is buried in the via hole to electrically connect the lower layer wiring and the upper layer wiring.

However, when a silicon oxide film constituting an interlayer insulating film is exposed to, for example, a chemical solution for removing a resist film at the time of etching, a hydrophilic silanol group (Si—OH) is formed in the thin film. There is a problem that a large number is formed and the hygroscopicity is increased. Therefore, if the interlayer insulating film absorbs moisture, the conductive layer is corroded or the insulating function of the interlayer insulating film is reduced. In addition, if moisture adheres to the surface of the interlayer insulating film or contains moisture therein, moisture is released from the interlayer insulating film when metal is buried in the via hole, and a gap between the lower wiring and the upper wiring is formed. The contact resistance is increased to cause a defect, and particularly, when a via hole is miniaturized with miniaturization of a semiconductor element, the influence thereof becomes remarkable.

As a countermeasure against the above problem, an interlayer insulating film is used.
A semiconductor substrate having a via hole formed therein is subjected to a pressure of 10^-8Tor
Heat treatment in a high vacuum of about r
It is possible to perform condensation and dehydration of the hydroxyl group to a high degree.
However, in this case, a pressure of 10 ^-8High vacuum of about Torr
Since it is necessary to use a decompression device to
Production costs increase and process control becomes difficult.
There was a problem of becoming.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to perform highly condensation and dehydration of silanol groups at around normal pressure (normal or slightly pressurized or slightly reduced pressure). In addition to preventing moisture absorption in the insulating thin film, preventing corrosion of the conductive layer and reducing the function of the insulating thin film,
An object of the present invention is to provide a semiconductor device and a method for manufacturing the same, which prevent an increase in contact resistance between a lower wiring and an upper wiring in a multilayer wiring structure.

[0007]

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: forming a wiring structure comprising at least one conductive layer on a semiconductor substrate via an insulating thin film; In the method, an insulating thin film formed by firing a hydrogen silsesquioxane resin is formed on the semiconductor substrate, and the insulating thin film is heated at a temperature of 150 to 550 ° C. in a pressure range of 1 to 1000 Torr. Is what you do.

[0008] A semiconductor device according to the present invention is characterized by being obtained by the above-described manufacturing method. The present inventors have performed a heat treatment in a specific temperature range around normal pressure on an insulating thin film obtained by firing a hydrogen silsesquioxane resin, whereby condensation and dehydration of silanol groups can be performed at a high level. I found something. This is due to the structure of the insulating thin film obtained by firing hydrogen silsesquioxane resin.
This is probably because the silanol groups are associated and can be eliminated with low energy.

That is, in the present invention, by performing the above-mentioned heat treatment on the insulating thin film obtained by firing the hydrogen silsesquioxane resin, only using a low-pressure depressurizing device near normal pressure or inexpensive, The silanol groups formed in the thin film can be sufficiently condensed, and the water attached to or contained in the thin film can be sufficiently dehydrated. Therefore, it is possible to prevent moisture absorption in the insulating thin film of the semiconductor device, thereby suppressing corrosion of the conductive layer and deterioration of the function of the insulating thin film. Also, when manufacturing a semiconductor device in which conductive layers having a multilayer wiring structure are electrically connected via via holes, it is possible to reduce the amount of water released from the insulating thin film when embedding metal in the via holes. Therefore, it is possible to prevent an increase in contact resistance between the lower wiring and the upper wiring.

In the present invention, the insulating thin film obtained by firing the hydrogen silsesquioxane resin is such that a part or all of the hydrogen silsesquioxane resin is silica (SiO ₂ ).
It has been converted to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 illustrates a method for manufacturing a semiconductor device having a multilayer wiring structure according to an embodiment of the present invention. First, as shown in FIG. 1A, a BPSG film is deposited on the entire surface of a semiconductor substrate (silicon wafer) 1 having a semiconductor element (not shown) formed on the surface, and the BPSG film is reflowed to form a base insulating film 2. I do. Next, a metal such as aluminum is sputtered on the base insulating film 2 to form a conductive layer, which is patterned by a known method to form the lower wiring 3.

Next, a solution obtained by dissolving the hydrogen silsesquioxane resin in a solvent is applied to the entire surface of the semiconductor substrate 1 by spin coating, and the hydrogen silsesquioxane resin is heated or irradiated with high energy rays. By curing, the interlayer insulating film 4 having a flat surface is formed. Then, the interlayer insulating film 4
A resist film 5 made of an organic resin is formed thereon, and the resist film 5 is patterned so as to provide an opening 5 a in a region immediately above the lower wiring 3.

Next, as shown in FIG. 1B, reactive etching (CF ₄ /
O ₂ ) to selectively etch the interlayer insulating film 4,
A via hole 6 reaching the lower wiring 3 is opened. next,
As shown in FIG. 1C, after the resist film 5 is removed by oxygen plasma treatment, the resist film 5 is treated with an alkaline liquid to completely remove the remaining resist film and oxides of the resist film, and the surface is further washed. ,dry.

In the step of removing the resist film, silanol groups may be generated in the interlayer insulating film 4. Therefore, the semiconductor substrate 1 provided with the via holes 6 is subjected to a heat treatment for 1 minute to 1 hour, preferably 5 to 20 minutes using a low-pressure vacuum device. In this heat treatment, the pressure is in the range of 1 Torr to 1000 Torr, and the heating temperature is in the range of 150 to 550 ° C, preferably 150 to 450 ° C.

Next, as shown in FIG. 1D, a conductive layer is formed by sputtering a metal such as aluminum on the entire surface, and this is etched back to leave the interlayer wiring 7 in the via hole 6. Next, an upper wiring 8 and an interlayer insulating film 9 are formed on the etched back surface in the same manner as the lower wiring 3 and the interlayer insulating film 4. In this way, a multilayer wiring structure including the lower wiring 3 and the upper wiring 8 can be formed on the semiconductor substrate 1.

According to the above-described method for manufacturing a semiconductor device of the present invention, the above-mentioned heat treatment is performed on the insulating thin film (interlayer insulating film 4) obtained by firing the hydrogen silsesquioxane resin, so that the thin film is formed in the thin film. The formed silanol groups can be sufficiently condensed and converted into siloxane bonds (Si-O-Si), and the moisture attached or contained in the thin film can be sufficiently dehydrated and removed due to the presence of the hydrophilic silanol groups.

Accordingly, moisture absorption in the insulating thin film can be prevented, so that a highly reliable semiconductor device in which corrosion of the conductive layer and deterioration of the function of the insulating thin film are suppressed can be obtained. In addition, in the manufacture of a semiconductor device having a multilayer wiring structure, it is possible to reduce the amount of water released from an insulating thin film when a metal is buried in a via hole, so that the contact resistance between the lower wiring and the upper wiring is reduced. The increase can be prevented, and the occurrence of a defect called a so-called poisoned via can be prevented. Moreover, since the contact resistance between the wirings can be suppressed as described above, the semiconductor element can be further miniaturized.

Further, the heat treatment may be carried out at a normal pressure or a slightly pressurized state, or at a pressure of 1T even if a decompression device is used.
Since the process is performed using an inexpensive decompression device that only needs to achieve a low vacuum state of orr or more, the manufacturing cost of the semiconductor device does not increase and the process control is easy. In the present invention, the pressure during the heat treatment needs to be in the range of 1 to 1000 Torr. When this pressure exceeds 1000 Torr, condensation and dehydration of silanol groups become insufficient,
If the pressure is less than 1 Torr, the cost of the decompression device may increase or the device may be adversely affected. The heating temperature is in the range of 150 to 550 ° C., preferably 150 to 550 ° C.
It must be in the range of 50 ° C. If the heating temperature is lower than 150 ° C., condensation and dehydration of silanol groups become insufficient. On the other hand, if the heating temperature is higher than 550 ° C., there are disadvantages such as an increase in heat treatment cost and an adverse effect on the device.

The heat treatment time is preferably from 1 minute to 1 hour. If the heat treatment time is less than 1 minute, condensation and dehydration of silanol groups become insufficient, and if it exceeds 1 hour, no further effect can be expected. The atmosphere during the heat treatment is not particularly limited, and may be an atmosphere of an inert gas such as nitrogen, air, or argon, steam, high-concentration oxygen, or an alkaline gas.

The hydrogen silsesquioxane resin is a polymer represented by the general formula (HSiO _3/2 ) _n (n: an integer). The insulating thin film can be formed by applying a solution obtained by dissolving a hydrogen silsesquioxane resin in a solvent onto a base material by a spin coating method and baking the applied solution. Since the molecular weight of hydrogen silsesquioxane resin is larger than the molecular weight of polysilicic acids and the like, the advantage that the SOG film using hydrogen silsesquioxane resin as a starting material can be formed thicker than other inorganic SOG films. There is.

The solvent for dissolving the hydrogen silsesquioxane resin is not particularly limited. Examples of the solvent include aromatic solvents such as toluene and xylene; aliphatic solvents such as hexane, heptane and oxane; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone (MIBK); and ester solvents such as butyl acetate and isoamyl acetate. Solvent, chain siloxane such as 1,1,1,3,3,3-hexamethyldisiloxane, 1,1,3,3-tetramethyldisiloxane, 1,1,3,3,5,5,7 , 7-
Octamethyltetracyclosiloxane, 1,3,5,7
A silicone-based solvent such as a cyclic siloxane such as tetramethyltetracyclosiloxane; a silane compound such as tetramethylsilane and dimethyldiethylsilane; and a mixture of two or more of the above solvents.

The above-mentioned solution may contain other additives and a curing accelerator. Additives include amylbenzene, isopropylbenzene, 1,2-diethylbenzene, 1,3-diethylbenzene, 1,4-diethylbenzene, cyclohexylbenzene, dipentene, 2,6
Hydrocarbon solvents such as dimethylnaphthalene, p-cymene, show brain oil, solvent naphtha, cis-decalin, trans-decalin, decane, tetralin, turpentine oil, kerosene, dodecane, dodecylbenzene (branched type) and cyclohexylbenzene; Ketone / aldehyde solvents such as acetophenone, isophorone, holone, methylcyclohexanone, methyl-n-heptylketone, diethyl phthalate, benzyl acetate, γ-butyrolactone, dibutyl oxalate, 2-ethylhexyl acetate, ethyl benzoate, benzyl formate, etc. Ester solvent, diethyl sulfate,
Examples include sulfolane, halogenated hydrocarbon solvents, alcohol solvents, polyhydric alcohol solvents, carboxylic anhydride solvents, phenol solvents, and silicone solvents. Further, as the curing accelerator, for example, a compound containing platinum such as chloroplatinic acid hexahydrate can be used.

According to the present invention, a via hole is formed by etching an insulating thin film using a resist film made of an organic resin as a mask, the resist film is removed by oxygen plasma, and the resist film and the resist remaining by treating with an alkaline liquid are further removed. This is particularly effective when oxides and the like of the film are completely removed. As an alkaline remover for a resist film made of an organic resin, it is preferable to use an aqueous solution of 2- (2-aminoethoxy) ethanol / hydroxyamine, a dimethyl sulfoxide solution of aminoethanol, or the like.

[0024]

EXAMPLE A semiconductor device was actually manufactured by the method for manufacturing a semiconductor device according to the examples of the present invention and the comparative example. Example: A hydrogen silsesquioxane resin was synthesized according to the method described in Example 1 on page 3 of JP-B-47-31838. This hydrogen silsesquioxane resin is disclosed in
The molecular weight was fractionated according to the method described in Example 1 on page 5 of 157760 to obtain a fraction having a number average molecular weight of 5830, a weight average molecular weight of 11,200 and a softening point of 180 ° C. This fraction was dissolved in methyl isobutyl ketone to prepare a solution having a solid content of 18% by weight. From this solution, an interlayer insulating film of a semiconductor device having an aluminum multilayer wiring structure (wiring pattern having a step height of 0.5 μm, a step width and a step interval of 0.18 μm each) was formed on a silicon wafer.

As a specific method of forming the interlayer insulating film,
After the base step is covered with the CVD film, the solution is placed on a silicon wafer at a pre-rotation speed of 500 rpm for 3 seconds.
Then, spin coating was performed at a main rotation speed of 5000 rpm for 10 seconds, and after the solvent was sufficiently evaporated, the film was allowed to stand at room temperature for 10 minutes to form a film of 8010 ° at the deepest part. The wafer is placed in a quartz furnace under a stream of nitrogen for 40 minutes.
It was baked at 0 ° C. for 1 hour.

Next, a resist film made of a novolak resin-based positive resist is patterned on the silicon wafer, and reactive etching (CF ₄ / O ₂ ) is performed using the resist film as a mask to form a via hole in the interlayer insulating film. Opened. Next, the resist film was removed by oxygen plasma treatment, the wafer was immersed in an amine-based registry remover composed of an aqueous solution of 2- (2-aminoethoxy) ethanol / hydroxyamine for 15 minutes, washed with alcohol, and washed at 100 ° C. for 10 minutes. Dried for minutes. And
This wafer is heated at 400 ° C. under normal pressure in air for 1 hour.
Heat treatment was performed for 0 minutes.

Comparative Example: An interlayer insulating film was formed on a silicon wafer in the same manner as in the above example. Next, a resist film made of a novolak resin-based positive resist was formed on the silicon wafer by patterning, and reactive etching (CF ₄ / O ₂ ) was performed using the resist film as a mask to open a via hole in the interlayer insulating film. Next, the resist film was removed by oxygen plasma treatment, the wafer was immersed in an amine-based registry remover composed of an aqueous solution of 2- (2-aminoethoxy) ethanol / hydroxyamine for 15 minutes, washed with alcohol, and washed at 100 ° C. for 10 minutes. Dried for minutes.

The infrared absorption spectra of the insulating thin films obtained in these Examples and Comparative Examples were measured, and the results are shown in FIGS. 2 and 3, respectively. 2 and 3
In the graph, the vertical axis indicates absorbance, and the horizontal axis indicates wave number (cm ^-1 ). As shown in FIGS. 2 and 3, it can be seen that the absorbance at 2900 to 3800 cm ⁻¹ attributed to silanol and water is reduced.

Further, the insulating thin films of the semiconductor devices obtained in Examples and Comparative Examples were further heated, and the amount of dehydration was measured by thermal desorption gas analysis (TDS). As a result, the amount of dehydration from the insulating thin film of the example was 7.6 × 10 ²¹ at.
om / cm ³ . On the other hand, the amount of dehydration from the insulating thin film of the comparative example was 1.3 × 10 ²² atom / cm ³ . Further, when the contact resistance between the lower layer wiring and the upper layer wiring was measured for the semiconductor devices obtained by the example and the comparative example, the contact resistance of the semiconductor device of the example was lower than that of the semiconductor device of the comparative example by 1 /. It was reduced to 10.

[0030]

As described above, according to the present invention, in a method of manufacturing a semiconductor device in which a wiring structure comprising at least one conductive layer is provided on a semiconductor substrate via an insulating thin film, An insulating thin film formed by firing hydrogen silsesquioxane resin is formed.
By performing the heat treatment at a temperature of 150 to 550 ° C. in the range of 1000 Torr, condensation and dehydration of silanol groups can be performed at a high pressure near normal pressure.

Therefore, it is possible to prevent moisture absorption in the insulating thin film of the semiconductor device, thereby suppressing corrosion of the conductive layer and deterioration of the function of the insulating thin film. Since it can be reduced, it is possible to prevent the occurrence of defects due to an increase in contact resistance between the lower wiring and the upper wiring.

[Brief description of the drawings]

FIGS. 1A to 1D are cross-sectional views showing steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an infrared absorption spectrum of an insulating thin film of a semiconductor device obtained according to an example of the present invention.

FIG. 3 is a diagram showing an infrared absorption spectrum of an insulating thin film of a semiconductor device obtained by a comparative example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate (silicon wafer) 2 base insulating film (BPSG film) 3 lower wiring 4, 9 interlayer insulating film 5 resist film 6 via hole 8 upper wiring

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyotaka Sawa 2-2 Chikusa Beach, Ichihara City, Chiba Prefecture Toray Dow Corning Silicone Co., Ltd. R & D Headquarters (72) Inventor Motoi Sasaki Chikashi Coast No. 2 in Ichihara City, Chiba Prefecture 2 Toray Dow Corning Silicone Co., Ltd. Research and Development Headquarters (72) Inventor Katsumi Mine 2-2 Ichihara City, Chiba Pref.

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device having a wiring structure comprising at least one conductive layer on a semiconductor substrate via an insulating thin film, wherein a hydrogen silsesquioxane resin is fired on the semiconductor substrate. An insulating thin film is formed and the insulating thin film is formed at a pressure of 1 to 1000 Torr for 15 minutes.
A method for manufacturing a semiconductor device, comprising performing heat treatment at a temperature of 0 to 550 ° C. 2. The method of manufacturing a semiconductor device according to claim 1, wherein said heat treatment time is 1 minute to 1 hour. 3. The insulating thin film is etched using a resist film as a mask to form a via hole, and is further treated with an alkaline liquid before the heat treatment. Further, the conductive layer is electrically connected between the layers through the via hole. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is electrically connected. 4. A semiconductor device obtained by the manufacturing method according to claim 1.