JP3150378B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a semiconductor device and, more particularly, to a method for manufacturing the same.

[0002]

2. Description of the Related Art In order to protect element elements of a semiconductor device, the element is formed and then covered with a protective insulating film. Here, the protective insulating film is formed by a CVD method, a sputtering method, a liquid phase growth method, or the like in the same manner as a normal insulating film. In addition to the protective insulating film, the insulating film is subjected to a process such as etching after forming a desired mask to form a large number of lead-out electrodes and wiring contact holes.

[0003]

As described above, the protective insulating film formed by the deposition method has a rough film structure and often exhibits hygroscopicity and moisture permeability. With such a protective insulating film, penetration of moisture cannot be prevented, and the moisture causes an oxidation corrosion reaction of the electrode wiring to cause corrosion of the wiring and oxidized substances to be deposited on the surface of the wiring to cause conduction failure.
Further, the charge retention characteristics of the semiconductor device often deteriorate due to moisture.

In addition, when an insulating film is opened to form an electrode and a contact hole is provided, the insulating film, which also exhibits hygroscopicity and moisture permeability, is exposed on the side wall of the contact hole, and the penetration of moisture and the formation of the electrode after the electrode formation. There is a possibility that a defect due to an oxidation corrosion reaction or the like may occur. Further, even when the insulating film itself has no hygroscopicity, a problem of surface leakage between the electrodes occurs when moisture on the surface of the insulating film is adsorbed.

[0005] These problems become more pronounced when the semiconductor device is left unmanaged during the manufacturing process due to stagnation or the like, so that strict process control is indispensable. Therefore, there has been a strong demand for a method of easily performing a moisture-resistant treatment and a water-repellent treatment on the surface of the insulating film.

[0006]

In order to solve the above-mentioned problems, the present invention provides a method for forming an element in a semiconductor device, comprising the steps of:
Forming an insulating film on the semiconductor substrate, and forming a water-repellent film on the surface of the insulating film, wherein the insulating film is an insulating film below the outermost layer; and The step of forming a coating film, an organic silicon compound having a lower specific gravity than the etching solution or the cleaning water and the etching solution or the cleaning water are stored in a single tank, and the insulating film is selectively etched. A method of manufacturing a semiconductor device, wherein the water-repellent film is formed by passing the semiconductor substrate through the silicon compound layer when the semiconductor substrate is pulled up from the etching solution or the cleaning water.

[0007]

[0008]

[Function] By forming a water-repellent coating on the surface of the insulating film, the penetration of moisture into the insulating film is strongly prevented, the corrosion reaction of the electrode wiring is suppressed, and the deterioration of the charge retention characteristics due to the moisture is prevented. To prevent and improve the moisture resistance of the element. Also,
Contamination of metals and the like can also be prevented.

Furthermore, not only moisture absorption and moisture permeability, but also adsorption of moisture on the surface of the insulating film is prevented, and surface leakage between electrodes on the insulating film is suppressed because the organosilicon compound is a good insulating material. .

Further, even when an opening is provided for an electrode or the like in the insulating film, a water-repellent coating is formed on the surface of the insulating film exposed on the side wall of the hole, so that the insulating film can absorb and absorb moisture. Moisture can be prevented, and the durability of the element can be improved.

[0011]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described in detail. In this embodiment, the present invention is applied to an EPROM.

As the organosilicon compound used in the present invention, for example, polydiorganosiloxane in polyorganosiloxane (hereinafter referred to as silicone) is shown in FIGS. Silicone can be classified into three basic types, oil, rubber, and resin, depending on its properties. Among them, FIG. 4 shows a chain molecular structure of silicone oil, where 1 is an integer of 0 or more, and FIG. Indicates a cyclic molecular structure,
m represents an integer of 3 or more. Here, R is the same or different, substituted or unsubstituted monovalent hydrocarbon group, mainly a methyl group (CH ₃ ), a phenyl group (C ₆ H ₅ ), a long-chain alkyl group (C _n H _{2n + 1} ), trifluoropropyl group (CF ₃
CH ₂ CH ₂ ).

The case where the present invention is applied to an EPROM device will be described with reference to FIGS. Figure 1 shows EP
FIG. 2 is a plan view showing a part of the ROM, FIG. 2 is a cross-sectional view showing a part of a cross section along AA ′ in FIG. 1, and FIG. 3 is a cross-sectional view showing a cross section along BB ′ in FIG.

EPROMs are formed using conventional methods. That is, first, an element isolation region 9 for isolating a memory cell on the surface of the semiconductor substrate 1 by a method such as the improved LOCOS.
Is formed to a thickness of about 800 nm. Thereafter, for example, a first gate insulating film 3 of about 30 nm is formed in the element planned region using hydrochloric acid, and for example, boron is introduced at a concentration of about 1 × 10 ²³ cm ⁻³ by ion implantation or the like, and the channel region is formed. 8 is formed. Next, for example, a first polysilicon layer for forming the floating gate 4 is deposited on the entire surface of the first gate insulating film 3 to a thickness of about 400 nm by a CVD method, and an impurity is doped at a concentration of 1 × 10 ^20.
Diffuse about 10 ²¹ cm ^-3 . Further, the first polysilicon layer and the first gate insulating film 3 are removed on the element isolation region 9 by using a dry etching method or the like, and a slit region 10 for separating the floating gate 7 is formed. After this, 90
An oxidation process is performed at a temperature of 0 ° C. or more to form a second gate insulating film 5 on the first polysilicon layer to a thickness of about 40 nm. Subsequently, a second polysilicon layer having a thickness of about 400 nm is deposited on the second gate insulating film 5 by using a CVD method or the like.
Impurity concentration in the polysilicon layer of 1 × 10 ²⁰ -10 ²¹ cm ^-3
Introduce a degree.

Next, a second etching is first performed by dry etching.
Is etched to form a control gate 6 extending over the channel region 8 and a slit region 10. Next, the second gate insulating film 5 and the first polysilicon layer are etched using a self-alignment technique,
The floating gate 4 is formed below the control gate 6.
Further, a step of forming peripheral elements may be included in the middle of the above steps.

Next, arsenic ions of about 1 × 10 ¹⁵ cm ⁻² are implanted by self-alignment using the control gate 6 and the floating gate 4 as a mask, and the source region 2 a and the drain region are formed on the semiconductor substrate 1 sandwiching the control gate 6. 2b is formed. Finally, a protective insulating film 7 is deposited on the entire surface by using a CVD method or the like, thereby forming an EPROM.

After the formation of the protective insulating film 7, it is immersed in a silicone oil bath and dried by heating to form a very thin water-repellent coating 11 of silicone or the like on the protective insulating film 7.
When the heating and drying are performed, the process can be completed quickly, and the work can be made more efficient. Here, silicone is applied on the protective insulating film 7 by immersion in a silicone oil bath, but silicone oil may be spray applied. In addition, although the coating is dried by heating after application, air drying and natural drying may be used, and the effect is not changed even if the coating is kept wet without drying.

In addition, if the water-repellent coating 11 is formed after the water bake-out by the heat treatment, even if the insulating film which has been absorbed once by the heat treatment is performed at 100 ° C. or more before the silicone coating, the storage in the state having a low moisture content is performed. Becomes possible.

FIG. 6 shows the result of measuring the charge retention of the EPROM in order to confirm the degree of moisture absorption and moisture permeability. If moisture is contained in the insulating film, the moisture may cause a loss of the insulating property and lower the charge retention. Here, a PSG film is used as a protective insulating film, left for 24 hours at room temperature in an atmosphere of 100% humidity, and left at a high temperature of 300 ° C., where 61 is a conventional example in which a water-repellent film is not formed, and 62 is a conventional example. It is a result when the present invention is used. Conventional example 6
In the case of No. 1, the charge retention characteristics rapidly deteriorate with leaving, whereas in the case of using the present invention 72, almost 100%
It was confirmed that the charge retention of the sample was maintained and that the sample was excellent in moisture resistance.

FIG. 7 shows a silicon oxide film formed on a semiconductor substrate by plasma CVD using tetraethyl orthosilicate at 450.degree. C., and after baking out water, forming a water-repellent film. And into the atmosphere 16
It is a measurement result of the water content in the insulating film when left for 8 hours. The horizontal axis indicates the temperature during vacuum heating, the vertical axis indicates the partial pressure of water in the released gas, and 71 indicates a conventional example having no water-repellent coating.
2 shows the result when the present invention was used. As is apparent from the figure, the conventional example 71 has a peak of water release at 100 ° C. to 200 ° C., and the amount of water release is extremely large even at other temperatures. Almost no release was detected, indicating that the water-repellent coating strongly prevented moisture absorption and permeation into the oxide film. Here, the oxide film is deposited by the CVD method.
There are a sputtering method, a liquid phase growth method, a coating method, and the like. Similar results were obtained with an insulating film having a water-repellent film formed by these deposition methods. Further, the water-repellent film formed as described above was excellent in electric insulation, and was able to suppress surface leakage between electrodes on the insulating film.

In particular, when a water-repellent film is formed on the protective insulating film, it is effective in preventing moisture absorption and moisture transmission during the subsequent wafer back grinding step, wafer cutting step, inspection step, and sealing step. . Alternatively, by performing the water-repellent film forming step of the present invention as a step before the above steps, moisture absorption and moisture transmission between the steps can be prevented, and durability can be improved.

Although an example of an EPROM has been described above, the present invention can also be used as a coating on an insulating film of various semiconductor devices such as a MOS FET. In addition, by using the present invention as a step before the encapsulation step, it is possible to improve the durability of the semiconductor element and prevent a change in characteristics. (Embodiment 2) Hereinafter, a second embodiment of the present invention will be described in detail. In this embodiment, the present invention is used in a step of opening a contact hole or the like.

By the conventional method, the MOS shown in FIG.
Form a type FET. That is, an element isolation region 53 is formed on a semiconductor substrate 51 by a normal LOCOS process, and a gate insulating film 54 having a film thickness of about 30 nm is formed in an element expected region by using a CVD method or the like. Next, polysilicon or the like is deposited to a thickness of about 400 nm, and etching is performed using a predetermined gate pattern as a mask to form a gate electrode 55. Thereafter, the gate electrode 55 as a mask, arsenic 2 × 10 ¹⁵ cm ^-2
The source region 52a and the drain region 5
2b is formed, and an insulating film 56 of about 200 nm is deposited.

Next, the source region 52a and the drain region 5
The contact hole 57 is formed by etching the gate insulating film 54 and the insulating film 56 on 2b. Here, if the insulating film 56 has hygroscopicity and moisture permeability, the side wall of the contact hole 57 is liable to be permeated with moisture or contaminated by metal or the like, and there is a possibility that the element characteristics will be deteriorated and the electrode material will be corroded later.

Then, an insulating film processing solution such as an etching solution and silicone oil are put into one tank, and since the specific gravity of the silicone oil is less than 1, contact holes are formed in a processing tank having two layers of the processing solution and silicone oil. After immersing the semiconductor substrate 51 in a portion excluding the portion 57 and performing an etching process to form a contact hole 57, the semiconductor substrate 51 is formed.
A thin water-repellent film 59 can be formed on the side wall of the contact hole 57 by performing heat treatment by passing through the silicone oil layer at the time of lifting. Or, after the etching treatment, the water tank for washing is made of two layers of water and silicone,
After washing with water, a water-repellent coating 59 made of silicone may be formed by passing through a silicone layer. Of course, after the etching treatment, a water-repellent film can be formed by a method such as spray coating of silicone oil. Also,
The silicone oil was dried by heat treatment.
Natural drying may be used.

Next, after removing the water-repellent film 59 on the surface of the source region 52a and the drain region b, which are in contact with the electrode material, by an argon sputtering method or the like, as in the prior art, the electrode material such as Al A metal is deposited by a sputtering method or the like to form an electrode 58, thereby completing a MOS FET. The water-repellent coating 59 is thin and can be easily removed.

By forming the thin water-repellent film 59 on the side wall of the contact hole in this manner, moisture does not penetrate into the insulating film, and deterioration of device characteristics such as charge retention characteristics can be prevented. In addition, erosion and precipitation such as corrosion in the electrode material can be prevented. In addition, the water-repellent coating 59 can prevent contamination of metals and the like.

In the above, the case where the present invention is applied to a MOS type FET has been described. In addition, the present invention can be widely applied to a case where a step of opening a contact hole or an electrode pad is required.

[0029]

As is clear from the above description, by forming a water-repellent film on the surface of an insulating film, the water-repellent film repels water and can prevent moisture absorption and moisture permeation. As a result, changes in device characteristics such as charge retention characteristics, and corrosion reactions of electrode wiring and the like can be suppressed favorably. Further, the water-repellent coating can also effectively suppress contamination of metals and the like.

Furthermore, even in the case of an insulating film having no hygroscopicity or moisture permeability, the surface of the insulating film is prevented from adsorbing moisture, and at the same time, since the water-repellent coating has insulating properties, surface leakage between the electrodes is effectively suppressed.

In addition, even when an opening for an electrode or the like is provided in the insulating film, a water-repellent coating is formed on the surface of the insulating film exposed on the side wall of the hole, so that the insulating film in the middle of the process can be formed. It is possible to prevent moisture absorption and moisture permeation into the device, prevent a change in device characteristics, and improve the durability of the device. In addition, even if a delay occurs between the steps, moisture absorption and moisture transmission can be prevented because the water-repellent coating is formed on the surface of the insulating film.

[Brief description of the drawings]

FIG. 1 is a part of a plan view of an EPROM showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a part of a section taken along AA ′ in FIG. 1;

FIG. 3 is a sectional view showing a part of a section along BB ′ in FIG. 1;

FIG. 4 is a general formula of a linear polydiorganosiloxane. Here, R is the same or different, substituted or unsubstituted monovalent hydrocarbon group, mainly a methyl group (CH ₃ ), a phenyl group (C ₆ H ₅ ), a long-chain alkyl group (C _n H _{2n + 1} ),
And a trifluoropropyl group (CF ₃ CH ₂ CH ₂ ). L represents an integer of 0 or more.

FIG. 5 is a general formula of a cyclic polydiorganosiloxane. Here, R is the same or different, substituted or unsubstituted monovalent hydrocarbon group, mainly a methyl group (CH ₃ ), a phenyl group (C ₆ H ₅ ), a long-chain alkyl group (C _n H _{2n + 1} ),
And a trifluoropropyl group (CF ₃ CH ₂ CH ₂ ). M represents an integer of 3 or more.

FIG. 6 is an experimental result showing a charge retention ratio when left at a high temperature of 300 ° C. according to the first embodiment of the present invention.

FIG. 7 is an experimental result showing a partial pressure of water in a released gas when left in the air for 168 hours after forming an oxide film and heated in vacuum.

FIG. 8 is a sectional view showing a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 51 Semiconductor substrate 2a, 52a Source region 2b, 52b Drain region 3, 53 First gate insulating film 4 Floating gate 5 Second gate insulating film 6 Control gate 7 Protective insulating film 8 Channel region 9 Element isolation region 10 Slit region 11, 59 Water-repellent coating 54 Gate insulating film 55 Gate electrode 56 Insulating film 57 Contact hole 58 Electrode 61 These are the results of measuring the water content in the insulating film in the conventional example. 62 shows the result of measurement of the water content in the insulating film when the present invention was used. 71 This is the result of measuring the charge retention of a conventional EPROM. 72 shows the result of measuring the charge retention of the EPROM of the first example of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/316 H01L 21/312

Claims (1)

(57) [Claims] 1. A method for forming an element in a semiconductor device, comprising:
Forming an insulating film on the semiconductor substrate, and forming a water-repellent film on the surface of the insulating film, wherein the insulating film is an insulating film below the outermost layer; and The step of forming a coating film, an organic silicon compound having a lower specific gravity than the etching solution or the cleaning water and the etching solution or the cleaning water are stored in a single tank, and the insulating film is selectively etched. A method of manufacturing a semiconductor device, wherein the water-repellent coating is formed by passing the semiconductor substrate through the silicon compound layer when pulling up the semiconductor substrate from the etching solution or the cleaning water.