JPH02185021A - Method of forming polycrystalline silicon onto semiconductor substrate - Google Patents

Abstract

PURPOSE:To prevent the melting of a growth thin-film while obviating the generation of a pinhole by previously forming the growth thin-film through a CVD method of a substance being wetted excellently to silicon and having the melting point higher than silicon and spraying molten silicon onto the growth thin-film. CONSTITUTION:Molten silicon is sprayed onto the growth thin-film 10 composed of a substance having excellent wettability to silicon and the melting point higher than silicon by injection from a nozzle 13a while a semiconductor substrate A, on a surface of which the growth thin-film 10 is shaped through a CVD method, is turned in an inert gas atmosphere 12, thus forming a polycrystalline silicon layer 6 in required thickness. That is, since the growth thin-film 10 is shaped previously onto the semiconductor substrate A through the CVD method, both thin-film 10 and molten silicon have wetting characteristics when molten silicon is sprayed onto the thin-film 10 in the inert gas atmosphere 12, thus quickly attaching both thin-film 10 and molten silicon. The melting point of the growth thin-film is made higher than silicon at that time. Accordingly, the growth thin-film is not melted, and no pinhole is also generated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a so-called dielectric isolation substrate in which the elements are electrically isolated by an electrical insulator when manufacturing an LSI etc. that can withstand high voltage. forming a supporting layer for
The present invention relates to a method for forming a polycrystalline silicon layer on a semiconductor substrate, which is required when forming a low-resistance polycrystalline silicon layer (polysilicon layer) on a single-crystalline Si substrate to prevent element destruction due to noise.

(Prior Art) The basic means that have been adopted so far as a method of manufacturing, for example, a dielectric isolation substrate are as follows.

That is, as shown in FIG. 4(a), a 5iOz film 2 is first formed on a single-crystal silicon substrate l by means such as thermal oxidation, and then an opening 3 is formed by photolithography, and then as shown in FIG. 4(b). ), the monocrystalline silicon substrate 1 is etched from the opening 3 using an alkaline solution to form a V-shaped groove 4, and then the 5iOzl! By removing 2 and forming a new 5iOz film 5 as an electrically insulating film, the semiconductor substrate A
Furthermore, a CV was formed on the surface side of this 5iOz l1i5.
A polycrystalline silicon layer 8 having a smooth upper surface 6a is formed by applying polycrystalline silicon (poly-Si) using the D method (see FIG.
It is formed as shown in d).

Here, of course, the dielectric isolation substrate 7 formed in this way is obtained by polishing the single crystal silicon substrate l up to the removal line 8 in FIG. 1(d), as clearly shown in FIG. 1(e). As is known, the lower end 4a of the apex angle of the groove 4 in the shape of the letter 7 is ground away, and the next LSI manufacturing process is carried out in this way.

By the way, when using the above manufacturing method, since the polycrystalline silicon layer 8 is to be formed by the CVD method as described above, it not only takes a considerable amount of time, such as several hours, to form the layer. Since the dielectric isolation substrate 7 obtained as described above must be wafer-polished as described above, it must have sufficient strength as a support to withstand the external force applied during the polishing. Therefore, a thick polycrystalline silicon layer of about 200 to 500 pcm is required.

However, as described above, the polycrystalline silicon layer 6 is
If it were to be formed, it would be time consuming and extremely expensive as described above.

Therefore, the applicant has already sprayed molten silicon onto a semiconductor substrate on which an electrically insulating film has been formed on a single crystal silicon substrate in order to remove the defects of the above-mentioned CVD method, and at the same time applied rotation to the semiconductor substrate. proposed that it is possible to form polycrystalline silicon to the required thickness in a short period of time.

However, in this case, since the polycrystalline silicon layer and the 5iOz film which is the electrically insulating film have poor wettability, many pinholes 9 are generated especially at the grooves 4 as shown in FIG. becomes.

In order to solve this problem, the applicant did not directly spray high-temperature molten polycrystalline silicon onto the semiconductor substrate, but instead stacked a polycrystalline silicon thin film formed by the CVD method on the semiconductor substrate in advance. By spraying molten silicon on the surface, it improves wetting with the side receiving the spray, which prevents the formation of pinholes θ.
It was also proposed that by injecting molten silicon directly onto the semiconductor substrate, the effects of unwanted thermal distortion on the semiconductor substrate due to the temperature difference between the two could be absorbed and removed by the polycrystalline silicon thin film produced by the CVD method ( Special request 1986
-134175).

The above method can certainly produce some effects, but this is because the polycrystalline silicon thin film produced by the CVD method and the liquid-phase growth material as molten polycrystalline silicon that is sprayed onto it are the same material. Therefore, the polycrystalline silicon thin film is easily melted by the heat of the molten polycrystalline silicon, resulting in the formation of crystal pinholes. This requires the formation of a polycrystalline silicon thin film, and if such pinholes occur, cracks may occur in the dielectric isolation substrate during heat treatment later in the device manufacturing process. , which can also lead to product defects.

Furthermore, as mentioned above, even though there is a polycrystalline silicon thin film produced by the CVD method, it is melted by the sprayed molten silicon, thereby reducing the effect of thermal strain generation on the semiconductor substrate. becomes.

(Problems to be Solved by the Invention) The present invention has been studied in view of the above-mentioned conventional problems, and in the method of claim (1), instead of forming a polycrystalline silicon thin film by the CVD method, By forming a thin film grown by CVD in advance using a substance that wets silicon well and has a higher melting point than silicon, and then spraying molten silicon onto this, the thin film grown by the spray will not melt. The purpose is to eliminate the conventional problem of bottle holes by ensuring wettability.

Next, in the method of claim (2), in the method of claim (1), the molten silicon spray environment is not only made into an inert atmosphere, but also the atmosphere is changed by a vacuum pump or the like. By holding it under reduced pressure, the generation of pinholes is further suppressed, and the above-mentioned claim (
Similar to 1), the purpose is to absorb and eliminate the influence of thermal strain on the semiconductor substrate by the presence of the grown thin film.

(Means for solving the problem) In this application, in order to achieve the above purpose, claims (
In 1), a semiconductor substrate, on which a thin film of a substance with good wettability to silicon and a melting point higher than that of silicon is formed on the surface by CVD method, is rotated in an inert gas atmosphere. , wherein polycrystalline silicon is grown on a semiconductor substrate, characterized in that molten silicon is sprayed from a nozzle onto the grown thin layer of the above substance to form a polycrystalline silicon layer of a required thickness. Further, in claim (2), the inert gas atmosphere in claim (1) is not a mere atmosphere but an inert gas atmosphere under reduced pressure. This is its content.

(Function) In the method of claim (1), since a grown thin film is previously formed on the semiconductor substrate by the CVD method, when molten silicon is sprayed onto this in an inert gas atmosphere, both become wet. As the melting point of the grown thin film is higher than that of silicon, the grown thin film will not be melted, and as a result, no pinholes will be generated and the heat on the semiconductor substrate may be reduced. The influence of strain is also eliminated, and since the semiconductor substrate is rotated, the uniformity of the polycrystalline silicon is improved.

In claim (2), in addition to the content of claim (1), since polycrystalline silicon is sprayed in an inert gas atmosphere under reduced pressure, the inert gas, which is one of the causes of pinhole generation, is The influence of this can be removed by reducing the pressure, making it possible to further suppress the occurrence of pinholes.

(Example) If the undiscovered object is described in detail with reference to Fig. 1, Fig. 1(a)
(b) (c) substantially corresponds to the above-mentioned figures 4 (a) (b).
This is the same as the conventional example in (c), and hereinafter the same members will be described using the same reference numerals.

That is, after forming a 5iOz film 2 by thermal growth on a single crystal silicon substrate l having a (100) plane orientation and a thickness of about 500 pm, an opening 3 is formed on one main surface by photolithography in a desired pattern. Next, as shown in the figure (b), grooves 4 are formed in the single crystal silicon substrate l by etching, and the 5iOz Fs2 is removed to form a new electrically insulating film as shown in the figure (c). A semiconductor substrate A is obtained by forming a 5iOz film 5 as shown in FIG.

Next, in the present invention, CVD is applied to the surface of the semiconductor substrate A in advance.
By this method, a substance that has good wettability to silicon and has a higher melting point (1430°C) than silicon, such as Si
Figure 1 (
As shown in d), the grown thin film 10 is formed for several times. In the present invention, a polycrystalline silicon layer as shown below is further formed using a spray device 11 as shown in FIGS. 2 and 3. It is an attempt to obtain.

Here, to explain the spray device 11, the entire unit is provided in an inert gas atmosphere 12 such as a chamber supplied with an inert gas G, and a melting tank 13 disposed on the upper side has a lower end thereof. The nozzle 13a is opened downward, and the polycrystalline silicon 14 stored in the melting tank 13 can be heated and melted by a first heating source 15 such as a high-frequency heating coil on the side. A pressurized inert gas 16 is applied from the upper side of the tank 13, and the silicon melted by the pressurization flows through the nozzle 13.
It is configured to be injected downward from a.

Furthermore, the same device 11 is also located in an inert gas atmosphere 12, and is provided with a turntable 18 that can be heated by a second heating source 17 directly below the melting tank 13.
The table in question! The semiconductor substrate A, on which the grown thin film 1O is formed, is placed on the substrate device 18a which is in a horizontal state as shown in FIG.

On the other hand, in the spray device 11 shown in FIG. 3, a shutter 18 is installed horizontally between the nozzle 13a of the melting tank 13 and the substrate device 18a so as to be able to block the sprayed molten silicon. The points are different from those in Figure 2.

Therefore, in order to carry out the present invention using the spray device 11 described above, a semiconductor substrate A having a grown thin film 1O as described above is used.
is placed in the center of the substrate device 18a, it is heated to 1100°C to 1350°C by the second heating source 17, and the turntable 18 is operated to heat it to 50°C to 1100°C.
The polycrystalline silicon 14 in the melting tank 13 is turned into molten silicon by the first heating source 15, and this is injected from the nozzle 13a by the pressurized inert gas 18, thereby causing the above-mentioned rotating semiconductor to rotate. Growth thin film 10 on substrate A
Spray it on top.

When a molten silicon layer having a desired thickness and a smooth upper surface is deposited on the grown thin film 10 of the semiconductor substrate A by this spraying, the rotation of the turntable 18 is stopped and the second heating source 17 The polycrystalline silicon layer 6 is fixedly formed on the surface of the grown thin film 10 of the semiconductor substrate A by stopping the heating and cooling and solidifying the molten silicon layer. It is considered as the degree.

As shown in FIG. 1(e), the material obtained in this way is removed by grinding from the removal line 8 and then
The use of a dielectric isolation substrate as shown in f) is as described above for the conventional method.

Here, the spray device 71 with the shutter 18 shown in FIG.
1, the molten silicon containing impurities that enters from the tip of the nozzle 13a is removed from the shutter 18.
Then, this shutter 18
By opening the shutter 18, impurity-free molten silicon can be sprayed onto the grown thin film 10 of the semiconductor substrate A, and when a predetermined amount of molten silicon is sprayed, the shutter 18 is closed to ensure quantitative accuracy. It also becomes possible to perform highly controlled control.

Moreover, at this time, the molten silicon from the melting tank 13 is kept injected and is blocked by the shutter 19, and if a new semiconductor substrate A is replaced and placed on the substrate device 18a in this state, the shutter 18 is closed. This makes it possible to adopt a work procedure in which the substrate A is opened and sprayed, and therefore a desirable result can be obtained in terms of improving work efficiency.

Next, in the method of claim (2), in addition to simply supplying the inert gas G into the inert gas atmosphere 12, a vacuum pump P is connected to a chamber made of stainless steel, for example. Then, the pump P is operated to replace the inside of the chamber with an inert gas G to maintain the pressure inside the chamber at about less than 100 Torr, and in this inert gas atmosphere under reduced pressure, As explained in claim (1) above, molten silicon is sprayed to produce a polycrystalline silicon layer.

(Effect of the invention) Since the method of claim (1) can be carried out as described above, when manufacturing a dielectric isolation substrate, only a part of the CVD method is used and other main steps are carried out by liquid phase growth. By adopting this law, not only can costs be reduced, but also CVD
By selecting the material for the thin film grown by the method, it is possible to eliminate the problem of pinholes, and the thin film reduces the effect of thermal distortion due to temperature differences on the semiconductor substrate when high temperature molten silicon is sprayed. As a result, the cause of product defects can be eliminated.

In claim (2), since the molten silicon is sprayed in an inert gas atmosphere under reduced pressure, the occurrence of pinholes due to the presence of the inert gas is eliminated.
Further, desirable polycrystalline silicon can be formed.

[Brief explanation of the drawing]

FIGS. 1(a), (b), (c), (d), (e), and (f) are examples for explaining the method of forming polycrystalline silicon on a semiconductor substrate according to claims (1) and (2) of the present application. FIGS. 2 and 3 are vertical cross-sectional front explanatory views in order of the manufacturing process of the semiconductor substrate, and FIGS. b) (c) (
d) (e) is a longitudinal sectional front explanatory view of the semiconductor substrate in the order of manufacturing steps illustrated to illustrate a method of forming polycrystalline silicon on a semiconductor substrate by the conventional CVD method, and FIG. 5 shows a pinhole formed by the conventional method. FIG. 2 is a longitudinal sectional front view of a semiconductor substrate showing a generated state. 8... Polycrystalline silicon layer] O... Growing thin film 12... Inert gas atmosphere 13a, fist... Nozzle A... Semiconductor substrate agent, patent attorney Yoshio Saifuji

Claims (2)

[Claims] (1) A semiconductor substrate, on which a thin film of a substance that has good wettability to silicon and a melting point higher than that of silicon has been formed on the surface by CVD, is rotated in an inert gas atmosphere while growing a thin film of a substance that has good wettability to silicon and has a higher melting point than silicon. A method for forming polycrystalline silicon on a semiconductor substrate, characterized in that a polycrystalline silicon layer of a required thickness is formed by spraying molten silicon onto the growing thin film by jetting it from a nozzle. (2) While rotating a semiconductor substrate on which a grown thin film of a substance with good wettability to silicon and a melting point higher than silicon is formed by CVD on the surface in an inert gas atmosphere under reduced pressure, Forming polycrystalline silicon on a semiconductor substrate, characterized in that molten silicon is sprayed from a nozzle onto the grown thin film of the above substance to form a polycrystalline silicon layer of a desired thickness. Method.