JPH04125929A - Insulating film forming method of semiconductor device and semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The purpose of the present invention is to commercialize an interlayer insulating film that has excellent heat resistance, low dielectric constant, and excellent crack resistance regarding interlayer insulating films that constitute multilayer wiring of semiconductor integrated circuits. The following general formulas (1), (2) and (
3) has a structural unit represented by
A method for forming an insulating film of a semiconductor device is characterized by using a 2 to 3×10′ organic borosilicate resin.

(RSi03zz) −(BO3/□> l, -----
---------1...--(1) (R3i(h/z)
m (PO5/□). -・(2)(RS
i037□) -(BO3/□) fi(PO5/2)
o......-(3) Ni, and R is an alkyl group having 1 to 6 carbon atoms.

or fluoroalkyl group, man is 60-99: 40-1 m:o is 60-99: 40-1 m:n:o is 60-99: 20-0.5: 20-0
．． 5 [Industrial Application Field] The present invention relates to an interlayer insulating film constituting multilayer wiring of a semiconductor integrated circuit and a semiconductor device using the same.

The interlayer insulating film according to the present invention not only has excellent flatness of steps caused by multilayering when forming highly integrated semiconductor devices such as LSI and VLSI, but also has low dielectric constant, heat resistance, oxygen plasma resistance, It also has excellent crack resistance.

Therefore, by using this insulating film, a semiconductor device with high reliability can be realized.

[Conventional technology]

The degree of integration of semiconductor devices has improved and LSI and VLSI have been put into practical use, but this has been achieved by miniaturizing unit elements, and as a result, the minimum line width of wiring has become submicron (S).
ub-micron) pattern is used.

On the other hand, in order to prevent a decrease in capacitance due to miniaturization of wiring, the thickness of the wiring pattern needs to be as high as 6,000 to 1 μm, and as a result, the difference in level becomes larger and larger.

For this reason, there is a need for an interlayer insulating film that can provide excellent flatness when forming multilayer wiring.

In addition, as information processing speeds up, signal frequencies have reached GHz, and the insulating films of semiconductor devices that process such high-speed signals are required to reduce the signal propagation delay time (τ). As is clear from equation (4), it is necessary to use a material with a small dielectric constant.

τ=ε112/c−−−−−−−・−−−−−・・−・
(4) Here, ε is the dielectric constant of the insulating film, and C is the speed of light. Conventionally, inorganic insulating materials and organic polymer materials have been used as materials for interlayer insulating films.

That is, silicon dioxide (SiOz) + silicon nitride (St
Inorganic materials such as phosphorus silicate glass (PSG) are formed using a vapor phase growth method (abbreviated as CVD method), but when using the CVD method, the insulating film is thin and has a similar shape to the underlying layer. Because of this, the unevenness on the substrate surface is reproduced exactly as it is, causing disconnection and poor insulation of the wiring formed thereon.

Another problem is that inorganic materials generally have a large dielectric constant.

In addition, organic polymer materials such as polyimide and silicone resin are formed by a spin-coding method, which is effective for flattening the substrate surface, but polyimide There is a problem in that the resin in the film undergoes oxidation and thermal decomposition, and cranks occur due to distortion of the film.

Furthermore, silicone resins have the problem that cracks occur even in thin films of 5000 Å or less due to internal distortion of the film due to the curing reaction and thermal shock.

In order to solve these problems, the inventors have developed an organic silica borosilicate resin or an organic phosphorus borosilicate resin that has a structural unit represented by the formula (5) or (6) and has an average molecular weight of 5 x 102 to 1X10'. is proposed to use.

(SiO4z□) −(BO3/□)lI−−−−・
−・−・・−−−−−・(5) (SiOa/z) p
(BO3/ri q(PO5/2) r------(6
) where m:n is 99:1~40:60 p:q:r=70~30:15~40
: 15-40 The characteristics of these resins are: (1) excellent heat resistance; (2) excellent oxygen plasma resistance; (2) excellent crack resistance.

In other words, the insulating layer obtained by spin-coding and post-heat-treating these resins is a relatively soft glassy material, and since it does not contain organic components, there is no distortion due to oxidation even when heat-treated in a 0□ atmosphere. There is a characteristic that it does not occur.

Furthermore, since it melts at a relatively low temperature compared to conventional inorganic materials, it is possible to reduce internal distortion that occurs during curing.

Therefore, if these resins are used as an interlayer insulation film, 3
It can be used up to a thickness of approximately μ-thickness without cracking.

However, in order to cope with the increase in the speed of signals propagating to semiconductor devices and to reduce the signal propagation delay time, it is necessary to further lower the dielectric constant of the interlayer insulating film forming material. It was necessary to suppress fluctuations in

[Problem to be solved by the invention]

As mentioned above, the inventors have a structural unit represented by the above formula (5) or (6) as a material that has excellent heat resistance and 02 plasma resistance as well as excellent crank resistance.
It is proposed to use an organosilicon or organophosphorus borosilicon resin having an average molecular weight of 5 x 102 to 1X10'.

These resins have a dielectric constant of 4 to 5, and are similar to SiO□ and Si.
Although it is small compared to inorganic materials such as 3N4, for semiconductor devices used for high-speed signal amplification and switching, it is possible to form an interlayer insulating film using a material with an even lower dielectric constant and excellent crack resistance. This is desirable, and its practical application has been desired.

[Means to solve the problem]

The above problem is solved by the following general formula (1) as an interlayer insulating film.

An insulating film for a semiconductor device characterized by using an organic silica borosilicate resin, an organic phosphorus silica resin, or an organic phosphorus borosilicate resin having the structural units represented by (2) and (3) and having an average molecular weight of 5X102 to 3X10'. This can be solved by forming .

(R5i(hzz) -(BOszz) , 1----
−−−−−−−−−−− (1) (RSiO+z□)
-(PO5/□). −・・−−−111 concave one song−(2
)(R5i03zz) -(BO+zz) 11(PO
s/z) o ----------(3) where R is an alkyl group having 1 to 6 carbon atoms.

or fluoroalkyl group, m:n is 60-99:40-1 mho is 60-99:40-1 m:n:o is 60-99:20-0.5:
20 to 0.5 C action] The present invention uses organic borosilicon resin, organic phosphorus silicon resin, or organic phosphorus silica resin, which the inventors have previously proposed as a method to put into practical use an interlayer insulating film forming material with a small dielectric constant value. In the boron resin, the structural unit 5i04y□ is changed to R31(hz□ (where R is an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group).

In other words, the necessary conditions for an insulating film that constitutes a high-frequency semiconductor device are: ■ excellent heat resistance, ■ excellent plasma resistance, ■ low dielectric constant of the constituent materials, and ■ flatness. ■It has excellent crack resistance, and the material previously proposed by the inventors is ■.

■ and ■ are satisfied.

On the other hand, the present invention satisfies the condition (2) by sacrificing the characteristics (2) and (2) to a practical extent.

In other words, regarding the heat resistance (2), the temperature applied to the semiconductor element during the manufacture of Si semiconductor devices is at most 4.
50°C, and even lower in the case of compound semiconductor devices.

Therefore, the heat resistance of the insulating film only needs to satisfy 450°C.
The R51037□ structural unit (R is an alkyl group) has a heat resistance of about 550°C.

In addition, the plasma resistance shown in (2) also shows sufficient characteristics for practical use.

On the other hand, by changing 5ix4y□ to R31 (hz□) as a structural unit, the dielectric constant can be significantly reduced.
Moreover, hygroscopicity can be reduced.

That is, the dielectric constant of the previously proposed insulating material is 4 to 5 when dehydrated, and increases to 8 to 9 when moisture is absorbed, but the dielectric constant of the insulating material according to the present invention is 3 or less when dehydrated. Even when moisture is absorbed, it is as low as 4 or less.

The reason for this depends on the presence or absence of an alkyl group or a fluoroalkyl group.

That is, in an interlayer insulating film formed using a borosilicon resin, a phosphorus silica resin, a baked sand boron resin, or the like, water molecules are likely to coordinate with constituent units such as BO+/z and Po5y□.

In other words, for BO3/□, water (
HzO) molecules are easy to coordinate.

Regarding PO37□, phosphorus (P) and O are likely to form a hydrogen bond with O that constitutes the double bond of PO.

For these reasons, it is easy to absorb moisture, which increases the dielectric constant.

On the other hand, when 5iOa7□ is changed to R51037□ as a structural unit, the alkyl group or fluoroalkyl group exhibits water repellency, so this addition can reduce hygroscopicity and maintain a low dielectric constant of 2.8 or less. can do.

Furthermore, since it contains an organic group, it has increased flexibility and can be used up to a thickness of approximately 5 μm without cracking.

〔Example〕

Synthesis Example 1: (Boron resin) In 11 flasks, 14 methyltriacetoxysilane
0g to tetrahydrofuran (abbreviation THF) 500ml
73 g of triethyl boric acid was added thereto, and after heating under reflux for 3 hours, the solvent THF was distilled off to obtain a transesterification reaction product.

30mjl of methanol for this! After stirring at room temperature for 30 minutes, add 20+aj! of ion-exchanged water. was added dropwise and heated at 50°C for 3 hours to cause hydrolysis and polycondensation.

After the reaction was completed, methanol and water in the solution were removed, and the obtained low molecular weight resin was dissolved in butyl cellosolve to obtain a resin solution.

Synthesis Example 2: (Baked sand base resin) In a flask of 11, 0.0% of methyltriacetoxysilane was added.
5 moles of tetrahydrofuran (abbreviated as THF)
ml, 0.5 mol of trimethyl phosphoric acid was added thereto, and after heating under reflux for 3 hours, the solvent THF was distilled off to obtain a transesterification reaction product.

To this was added 50+ of methanol, and the mixture was stirred at room temperature for 15 minutes.

Add to this ion exchange water for 30 yen! was added dropwise and heated at 50°C for 3 hours to cause hydrolysis and polycondensation.

After the reaction was completed, methanol and water in the solution were removed from the resulting reaction mixture under reduced pressure, and ethyl lactate was added to adjust the concentration to obtain a resin solution.

Synthesis Example 3 (Burned Sand Boron Resin) In a 500N+J2 flask, 66g of methyltriacetoxysilane was dissolved in 250val of THF, 34g of triethoxysiborane was added thereto, and the mixture was heated under reflux for 3 hours. , the solvent TIF was distilled off to obtain a transesterification reaction product.

Next, in 12 other flasks, 66 g of tetraacetoxysilane was dissolved in 250 ml of THF, 35 g of trimethyl phosphate was added, and after heating under reflux for 3 hours, the solution was dissolved in THF.
was distilled off to obtain a transesterified product.

Mix this with the transesterified product from above, and add 50 volumes of methanol to this! After stirring at room temperature for 30 minutes, add 20/! of ion-exchanged water. was added dropwise and heated at 50°C for 3 hours to cause hydrolysis and polycondensation.

After the reaction was completed, methanol and water in the solution were removed, and the obtained low molecular weight resin was dissolved in butyl cellosolve to obtain a resin solution.

Example 1: The resin solution obtained in Synthesis Example 1 was applied to a Si substrate (with a wiring thickness of 1 μm) on which one wiring of the first layer was applied in the formation of a semiconductor element.
, a minimum line width of 1 μm and a minimum line spacing of 1°5 μl1) were coated using a spin code method at 3000 rpm for 30 seconds to form a coating film with a thickness of 1 μm.

The coating film was dried at 80°C for 20 minutes to remove the solvent, and then heated at 450''C for 30 minutes to polymerize.

The level difference on the substrate surface after the heat treatment was 0.2 μm or less, and the level difference caused by the first layer An wiring was flattened.

Next, through holes are formed on the substrate, and the second layer A
After forming N wiring and forming a 1.3 μm-thick phosphor glass layer as a protective layer, a window for taking out the electrodes was opened to obtain a semiconductor device.

No defects were observed in this device even after a heating test in the atmosphere at 500°C for 1 hour and a thermal shock test of 165°C to 150°C 10 times.

Example 2: Using the resin solution obtained in Synthesis Example 1, a resin layer with a thickness of 0.7 μm was formed on a Si substrate in the same manner as in the previous example, and phosphor glass was further applied on this by a known method. It was formed to a thickness of 0.5μ.

This film flattened the underlying step to 0.4 μm.

Next, a semiconductor device was manufactured and tested in the same manner as in Example 1, but no defects were observed.

Example 3: The resin solution obtained in Synthesis Example 1 was applied to a Si substrate with a first layer of poly-Si wiring (wiring thickness 1 μm, minimum line width 1 μm, minimum line spacing 1.5 μm) at 3000 rpm using the spin code method.

The coating was applied for 30 seconds to form a coating film with a thickness of 1 μm.

This coating film was dried at 80° C. for 20 minutes to remove the solvent, and then heated at 450° C. for 30 minutes to polymerize.

The level difference on the substrate surface after the heat treatment was 0.2 μm or less, and the level difference caused by the first layer poly-Si wiring had been flattened.

Next, through holes were formed on the substrate and treated with 2.5% hydrofluoric acid, followed by a second layer of poly-Si wiring, and a 1.3 μm thick phosphorous glass layer was formed as a protective layer. After forming, a window for taking out the electrodes was opened to obtain a semiconductor device.

No defects were observed in this device even after a one-hour heating test at 500°C in the atmosphere and 10 thermal shock tests at -65°C to 150°C.

Example 4: The resin solution obtained in Synthesis Example 2 was applied to a Si substrate with a first layer of An interconnection (wiring thickness of 1 μm) in the formation of a semiconductor element.
A coating film having a thickness of 1 .mu.m was formed by applying the coating onto a surface of 1 .mu.m, minimum line width: 1 .mu.m, minimum line spacing: 1.degree.

This coating film was dried at 80°C for 20 minutes to remove the solvent, and then heated at 450°C for 30 minutes to polymerize.

The level difference on the substrate surface after the heat treatment was 0.2 .mu.- or less, and the level difference caused by the first layer Aj2 wiring had been flattened.

Hereinafter, a semiconductor device was manufactured and tested in the same manner as in Example 1, but no defects were observed.

Example 5: Using the resin solution obtained in Synthesis Example 2, a resin layer was formed on a Si substrate to a thickness of 0.7 μm in the same manner as in Example 1, and phosphor glass was further applied on this layer using a known method. The film was formed to a thickness of 0.5 μm using the same method.

This film flattened the underlying step to 0.4 μm.

Next, a semiconductor device was manufactured and tested in the same manner as in Example 1, but no defects were observed.

Example 6 The resin solution obtained in Synthesis Example 2 was used to form a semiconductor element on a Si substrate with a first layer of poly-Si wiring (wiring thickness 1 μm, minimum line width 1 μm area, minimum line spacing 1.5 μm). ) using the spin code method at 3000 rpm+.

The coating was applied for 30 seconds to form a 1 μm thick steel coating.

A semiconductor device was manufactured and tested in the same manner as in Example 1, but no defects were observed.

Example 7: The resin solution obtained in Synthesis Example 3 was used to form the first layer of AI! in the formation of a semiconductor device. A coating film with a thickness of 1 μm was formed by applying the coating on a wired Si substrate (wiring thickness 1 μm, minimum line width 1 μm, minimum line spacing 1°5 μm) using the spin code method at 3000 rpm for 30 seconds. was formed.

A semiconductor device was manufactured and tested in the same manner as in Example 1, but no defects were observed.

Example 8: Using the resin solution obtained in Synthesis Example 3, a resin layer with a thickness of 0.7 μm was formed on a Si substrate in the same manner as in Example 1, and phosphor glass was further applied on this by a known method. It was formed to a thickness of 0.5 μm.

This film flattened the underlying step to 0.4 μm.

Next, a semiconductor device was manufactured and tested in the same manner as in Example 1, but no defects were observed.

Example 9: The resin solution obtained in Synthesis Example 3 was used to form a semiconductor element on a Si substrate with a first layer of poly-Si wiring (wiring thickness: 1 μm, minimum line width: 1 μm, minimum line spacing: 1.5 μm) at 3000 rpm using the spin code method.

The coating was applied for 30 seconds to form a coating film with a thickness of 1 μm.

A semiconductor device was manufactured and tested in the same manner as in Example 1, but no defects were observed.

〔Effect of the invention〕

By implementing the present invention, the dielectric constant is small and the heat resistance and zero resistance are reduced.
□It is possible to put into practical use an interlayer insulating layer that satisfies conditions such as plasma properties and flatness, and has better crack resistance than conventional ones, making it possible to manufacture high-frequency semiconductor devices.

Claims (6)

[Claims] (1) When forming multilayer wiring for semiconductor integrated circuits,
An insulation for a semiconductor device, characterized in that an organic borosilicate resin having a structural unit represented by the following general formula (1) and having an average molecular weight of 5 x 10^2 to 3 x 10^4 is used as an interlayer insulating film. Film formation method. (RSiO_3_/_2)_m(BO_3_/_2)_
n…………(1) Here, R is an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group, m:n is 60-99:40-1 (2) A semiconductor device characterized in that the organic borosilicate resin according to claim 1 is used as an interlayer insulating film. (3) When forming multilayer wiring for semiconductor integrated circuits,
An insulation for a semiconductor device, characterized in that an organic phosphorus silicon resin having a structural unit represented by the following general formula (2) and having an average molecular weight of 5 x 10^2 to 3 x 10^4 is used as an interlayer insulating film. Film formation method. (RSiO_3_/_2)_m(PO_5_/_2)_
o…………(2) Here, R is an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group, m:o is 60-99:40-1 (4) A semiconductor device characterized in that the organic phosphorus silicon resin according to claim 3 is used as an interlayer insulating film. (5) When forming multilayer wiring for semiconductor integrated circuits,
A semiconductor device characterized in that an organic phosphorus-silicon-boron resin having a structural unit represented by the following general formula (3) and having an average molecular weight of 5 x 10^2 to 3 x 10^4 is used as an interlayer insulating film. Insulating film formation method. (RSiO_3_/_2)_m(BO_3_/_2)_
n(PO_5_/_2)_o (3) Here, R is an alkyl group having 1 to 6 carbon atoms. or fluoroalkyl group, m:n:o is 60-99:20-0.5:20-0.5 (6) A semiconductor device characterized in that the organic phosphorus-silicon-boron resin according to claim 5 is used as an interlayer insulating film.