JPS6390137A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a highly reliable multilayer interconnection by a method wherein a low-energy surface whose contact angle in relation to n-hexadecane is partially more than 100 deg. is formed on the surface of a semiconductor device and an insulating material is deposited by a CVD method at a part other than that part. CONSTITUTION:An n-ch MOSFET is formed on a p-type Si substrate 21, and an Al wiring 26 is formed by making use of photoresist 27 as a mask. If the photoresist 27 is covered with a fluoride film by being exposed to an F plasma and CVD SiO2 28 is deposited at 100 deg. by pouring SiH4 and N2O, the SiO2 remains deposited selectively on PSG 25 only. If the resist 27 is removed after that, a flat interlayer insulating-film 29 can be formed by an ordinary CVO method. As a result, a multilayer interconnection of high reliability can be obtained. Because, at the fluoridized resist 27, the surface energy is small and the adsorption probability of the SiH4 is small, the SiO2 is not deposited. The contact angle in relation to n-hexadecane as an index for the surface energy corresponds well to the adsorption probability of the SiH4, it is preferable to select a fluoridized resist surface whose contact angle in relation to the n-hexadecane is more than 100 deg..

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to semiconductor integrated circuit devices (IC). 5, and more specifically, it relates to a method for forming IC flat and highly reliable multilayer wiring.

[Conventional technology]

In recent years, high-performance multilayer interconnection technology in ICs has developed, for example, using extremely flat 5iO formed by bias sputtering.
It has become necessary to use Z films as interlayer insulating films. The reason for this is that as the density of ICs increases, the unevenness on the element surface cannot be ignored compared to the lateral dimension, and as a result, the possibility of poor step coverage due to the influence of the stepped portion increases. This is because it has become a cause of wiring defects at the ends.

[Problem that the invention seeks to solve]

In other words, in the conventional technology, as shown in FIG. 2, for example, a first conductor 13 is formed on a semiconductor substrate 11 through an insulating film 12, and then a chemical vapor deposition method (hereinafter abbreviated as CVD method) is used. In this state, an interlayer insulation 14 is deposited and a second conductor 15 is further formed. As the distance between the lines of the first conductors 13 becomes narrower, the thickness of the interlayer insulating film 14 becomes uneven depending on the location, and in particular, the thickness of the interlayer insulating film 14 becomes uneven in the recesses between the first conductors. The deposited film thickness becomes extremely thin. As a result, a short circuit occurs between the first conductor and the second conductor, or a break occurs in the second conductor 15.

A method of forming an interlayer insulating film using bias sputtering technology has been devised to prevent such defects in multilayer wiring. By depositing the interlayer film 16 formed by bias sputtering on the first conductor 13 formed on the semiconductor substrate 11 via the insulating film 12, a flat surface is obtained, and as a result, the second conductor 13 The four electric bodies 15 are formed without causing defects such as disconnections and short circuits. However, in this bias sputtering method, (1) an impact is applied with a charged beam, which damages already formed devices.

(2) Since the film is deposited while performing sputter etching, the film deposition rate is extremely slow. (3) In principle, a step larger than the original step is formed on a pattern that is wider than a certain level. There are problems with this, and it has not always been put into practical use.

To summarize the problems of the prior art once again, multilayer wiring in high-density ICs is extremely difficult due to defects in the interlayer insulating film and the second conductor layer caused by the step difference in the first conductor. It is necessary to effectively alleviate the influence of the step difference in the second conductor.

An object of the present invention is to disclose a technique for reducing the level difference caused by the second conductor by using the interlayer insulating film in a self-aligned manner in order to solve the problems of the prior art.

[Means for solving problems]

In order to achieve the above object, the present invention aims to selectively form an interlayer insulating film in the periphery of the first conductor to effectively remove the step formed by the second conductor. 6
In order to selectively form the interlayer insulating film, it is sufficient to use a chemical vapor deposition method (hereinafter referred to as CVD method) in which the interlayer insulating film is not deposited on the surface of the second conductor but is deposited only in the gap of the first conductor. .

[Effect]

The principle of the present invention will be explained using FIG. The organic substance p? present on the first conductor 3 formed on the silicon substrate 1 via the insulating film 2? When depositing SiO2 by CVD using monosilane (SiHa) and nitrous oxide (NzO) in Honmachi-zukuri with J4, nothing is deposited on the organic layer 4 and nothing is deposited on the insulating film 2. Deposition of 5iOz5 occurs.

After depositing the 5iOz to a film thickness almost the same as that of the second conductor 3, the organic layer 4 is removed, and then a normal CV
By further depositing an insulator using the D method, a flat interlayer insulating film can be formed, and as a result, a highly reliable multilayer wiring structure can be formed. The presence of the organic material layer is not necessarily essential, as long as the surface conditions on the second conductor 3 and the insulating film 2 are sufficiently different to cause a selective reaction of 5i025 deposited by the CVD. good. Due to this difference in surface condition, there are parts where the 5iOz5 is deposited and parts where it is not. In general, the surface energy is sufficiently small and deposition can be prevented by preventing gas adsorption during CVD.

〔Example〕

The present invention will be described in detail below based on examples.

Example 1 In this example, an interlayer insulating film was selectively formed on the insulating film by fluorinating the surface of the organic material formed on the surface of the second conductor with fluorine plasma to reduce the surface energy. Disclose a method to do so.

FIG. 4(a) shows a conventional n-channel MOS process (
Thickness: 0.8 μm by n-MOS process)
Element isolation oxide film 22 grown by thermal oxidation, thickness 2
0nm gate oxide film 20Paly deposited by CVD method
-Si gate 23, source/drain regions 24 formed by arsenic ion implantation. A phosphorus glass (psG) film 25 is formed using the AQ! !
j! A state in which the line 26 is processed using the upper 26 stroke 27 as a mask is shown.

FIG. 4(b) shows the structure exposed to fluorine plasma.

After forming a fluoride film on the surface of the photoresist 27, S i 1
The substrate was placed in a CVD furnace through which NxO gas was flowed, the substrate temperature was raised to 100°C, and a SiOx layer 28 was deposited. At this time, the surface of the resist 27 has 5iHa.
5 only on the surface of the PSG 25 because it will not be adsorbed.
iOz28 is deposited. The reason why the 5iOz 28 is not formed on the plasma fluorinated resist 27 is that monosilane is not adsorbed onto the fluorinated resist 27, and therefore no SiOx formation reaction occurs. That is, when the surface energy is small, the probability of gas adsorption becomes small. Fifth
As shown in the figure, normal hexadecane (n-hexadacar, hereinafter n-hexadacar) is an indicator of surface energy.
The contact angle for n-hexadecane (hexadecane) and the adsorption probability of monosilane show a good correspondence, and when the contact angle of n-hexadecane becomes 100 degrees or more, it shows a selective adsorption of 8 degrees, which enables one-selective growth. I understand. Therefore, in order to cause selective growth, it is necessary to make the surface energy of the sample surface at least 100 degrees or more at the contact angle with respect to n-hexadecane. FIG. 4C shows a state in which after the resist 27 is removed by oxygen plasma, a 5iOz layer 29 is further deposited by CVD to form a second conductor JW30.

The substrate temperature can be selected depending on the heat resistance of the resist 27 used as the organic material and the selectivity of one reaction. For example, if a polyimide-based organic material is used, the substrate temperature will be 400°C.
Although it is possible to raise the temperature to about 350°C, the appropriate temperature is about 350°C or lower because fluoride on the surface reduces the selectivity of the decomposition 1 reaction. Furthermore, when the temperature rises to 500° C. or higher, 5iHa decomposes in the gas phase, and the selectivity of the surface reaction decreases, making it impossible to selectively grow an insulating film, which is the gist of the present invention.

In the present invention, a mixed gas of 5iHa and N z O was used as the reaction gas, but in order to improve the selectivity of the reaction, a gas that is likely to be adsorbed on the surface can be selected.

For example, mixed gases such as dichlorosilane (S i HxCQz), chlorosilane (Si) (gcffi) and NzO increase selectivity, but disilane (S i zHe)
These compounds tend to decompose to form radicals such as 5iHa 2 and have high reactivity, making selective deposition difficult. Further, when pure oxygen is used as an oxidizing agent, the reactivity is high (SiOx is easily formed), so the selectivity is low, and it is unsuitable as a reaction gas.

Selective deposition by irradiation with ultraviolet light is also possible. In this case, for example, wavelength 3Q using xenon chloride (XeCQ)
It is also effective to use a laser beam such as an 8 nm excimer laser or an argon laser, or a multi-wavelength light source such as a xenon lamp or a mercury lamp. It is possible to selectively form 5ift by exciting the gas adsorbed on the surface with light. In this case as well, the magnitude of the surface energy is n
- A suitable contact angle for hexadecane is 100 degrees or less.

Example 2 This example discloses a method of creating a state of low surface energy through surface treatment to enable selective deposition.

FIG. 6(a) shows a thermal oxide film 22 grown by thermal oxidation on a P-type (100) 10Ω silicon substrate 21. After forming the first conductor layer 26, plasma is irradiated in a fluorine gas atmosphere to form silicon fluoride M! on the thermal oxide film. J31
, and a state in which an aluminum fluoride layer 32 is formed on the aluminum wiring 26, respectively.

FIG. 6(b) shows the structure formed in this way at approximately 40 mm.
heating to 0° C. to evaporate the silicon fluoride MJ31;
After leaving the aluminum fluoride layer 32 with low surface energy only on the aluminum 26, 5iHa and N x
5iOz layer 28 is deposited while heating the substrate temperature to 200° C. in a mixed gas atmosphere of O. At this time, the thermal oxide film 22 is deposited at a rate of 1000 per minute, and the aluminum fluoride layer 32 is deposited at a rate of 1000 per minute. 50 people were deposited every minute. Therefore, if the film thickness of the -th conductor) g126 is 1 μm, then 1
By depositing the 5iOz layer 28 for 0 minutes, it is possible to obtain a wiring structure similar to that of Sjt. Further, by depositing an interlayer insulating film 29 to a required thickness and forming a second conductive layer 30, the two-layer wiring is completed.

A wiring structure of three or more layers can be formed by further repeating the selective CVD of an insulating film, the deposition of an insulating film, and the formation of wiring. Furthermore, when forming a contact to the lower conductive layer, it is necessary to perform sputtering using argon (Ar) ions to remove defective conductive layers such as aluminum fluoride formed on the surface of the lower conductive layer. Needless to say.

In addition, the thickness of the selective insulating film is approximately the same as that of the conductive layer.
Although it is optimal in terms of reducing the level difference, if the film becomes too thick, problems such as cracks and stress will occur, so 1μ
It is not appropriate to make it more than m.4゜[Effect of the invention] According to the present invention, a completely flat multilayer structure tl&', 1
! It is possible to form l iN, which not only can almost completely prevent problems such as disconnections and short circuits, but also greatly improves reliability, which has great technical effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention, FIGS. 2 and 3 are explanatory diagrams of the prior art, and FIGS. 4 to 6 are diagrams illustrating the prior art. FIG. 1 is a diagram showing an example of the present invention. 1.11.21...Semiconductor substrate, 12,22.20.
... Insulating film, 5, 14, 16, 28. 29... Layer separation Figure 2 3n (I7) CC) Figure 5

Claims (1)

[Claims] 1. A process of partially forming a surface with low surface energy such that the contact angle with n-hexadecane is at least 100 degrees or more on a part of the surface of the semiconductor device, and forming the part with low surface energy by chemical vapor deposition. 1. A method for manufacturing a semiconductor device, comprising at least the step of depositing an insulator.