JPS58153349A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To isolate elements adapted for a high integration by forming a vertical groove in an Si substrate, covering SiO2 film, superposing polysilicon, etching to the boundary of the SiO2 film, then oxidizing the polysilicon and etching the SiO2 to the surface of the substrate. CONSTITUTION:Two layer mask of SiO2 22' and Si3N4 23' is formed on an n type Si substrate 21, etched by reactively sputtering to form a vertical groove, an SiO2 film 27 is covered, and an n type layer 26 is formed by ion implantation in the bottom of the groove. Polysilicon 27B is superposed by a CVD method through an SiO2 27A, a flat surface is formed, and the layer 27B is etched to the boundary of the layer 27A. The polysilicon 27B' which remain in the groove is converted into an SiO2 27B'', with the Si3N4 film 23' as a mask the films 27A, 27B'' are etched to the surface of the substrate, and when the films 23', 22' are then removed, no bird beak is produced, the surface is flat, and an element adapted for high integration can be isolated.

Description

DETAILED DESCRIPTION OF THE INVENTION This article a- relates to a method for manufacturing a conductor device O, 411K, and a method for manufacturing a conductor device O by separating its elements. A manufacturing process for element isolation using a selective oxidation method that utilizes the growth rate difference of oxide films formed on a silicon nitride film by a thermal oxidation method is shown in Marugame.

FIG. 1(a) shows II! of the silicon crystal substrate 11! A silicon dioxide film 12 is formed on the surface by thermal oxidation, then silicon 11ide 1[13 is formed thereon, and silicon nitride 1[1!] is further formed by thermal oxidation. After forming silicon dioxide fIAJl[14 on top, a photoresist 15 having an element region shape is formed to show nine states.

The first color value) uses photoresist 15 as a corrosion-resistant mask,
A state in which the photoresist 15 is removed after the silicon dioxide film 14 is etched away to form silicon dioxide@14' having the shape of an element region is shown.

FIG. 1 ((1) shows how silicon nitride l[15 is etched away using silicon dioxide film 14' as a corrosion-resistant mask to form a quantized silicon film 15' having an element region shape.
Using M' as a diffusion-resistant mask, an impurity 16 having the same conductivity as that of the substrate 11 is diffused into a non-element region to show nine states.

Figure 1 (a) Silicon nitride 11 [1! Thermal oxidation is performed using S' as an oxidation-resistant mask, and a thick silicon dioxide layer 17 is formed in the non-element region, indicating a good condition.

FIG. 1 (·) shows a good condition after removing the silicon dioxide film 14' and the silicon oxide film 1 and removing the element.

However, the conventional selective oxidation method for device isolation has the disadvantage that when forming a thick silicon dioxide film on a non-device region, a so-called bird's beak occurs and the width of the device region is narrowed.

At present, as elements become more integrated, the dimensions of the elements are gradually becoming smaller. Under these circumstances, the narrowness of the device region width O in device isolation by the selective oxidation method described above is a major problem. It is necessary to take into consideration the amount of sipper beater from the beginning and take into account the amount of silicon dioxide O added to the mask dimensions in advance, and ζ0 has a great effect on the Kf profile dimensions when manufacturing large-capacity integrated circuits.

The present invention prevents so-called bird's beak, which occurs when a thermal oxide film is grown for device isolation in a non-device region, and eliminates the narrowing of the device region width. The present invention provides a method for manufacturing a semiconductor device having an element isolation structure suitable for high integration by performing planarization.

That is, the present invention includes a step of forming silicon silicate by CVD in a hindlimb groove formed by etching a groove in a semiconductor substrate, a step of filling the groove with polycrystalline silicon to make the surface flat, a step of etching away polycrystalline silicon to below the silicon dioxide film interface so as to leave it in the groove, oxidizing the polycrystalline silicon left in the groove to form silicon dioxide down to the surface of the semiconductor substrate, and at the same time flattening the surface. This method is characterized by performing a step of etching the silicon dioxide film formed on the semiconductor substrate down to the surface of the semiconductor substrate.

A typical embodiment of the present invention will be described in detail below with reference to FIG.

In FIG. 2(1), silicon dioxide J[22] is formed on a silicon crystal substrate 21 by a thermal oxidation method, a silicon nitride film 23 is formed thereon, and a photoresist 25 having an element region shape is further formed. Shows the formed state.

In FIG. 2(b), the underlying silicon nitride film 21 is etched by reactive sputter etching using a photoresist 25 as a sputter etching-resistant mask. Figure 2(c) shows the state in which the silicon dioxide film 22 and the silicon crystal substrate 21 have been etched away, the groove A has been formed, and the photoresist 25 has been removed.
A silicon dioxide film 27 is formed on the surface of the trench A, and an impurity 24 having the same conductivity as the substrate is ion-implanted into the bottom of the trench using the silicon nitride film 2I' covering the element region as an ion implantation-resistant mask. show.

Section 211(d) is the CVD method K! D silicon dioxide 1
127jl is in good shape throughout. Due to the shape of the silicon dioxide film 27Al, the shape of the opening at the top of the groove becomes an inverted V-shape. Since the opening at the top of the groove forms an inverted V-shaped lid in this manner, polycrystalline silicon OH can be easily penetrated into the groove in the next step, and the surface can be made flat.

No. 211 (@) shows a state in which 273% polycrystalline silicon is grown over the entire surface, the grooves are completely deepened, and the surface is made flat.

The second image 1(f) shows the state in which the polycrystalline silicon 17B is removed by etching below the silicon dioxide film 27Aj9.

Figure 2 (b)) shows the polycrystalline silicon 27B left in the groove.
' is oxidized by a thermal oxidation method to form silicon dioxide 27B#, and the surface is planarized. However, at this time, the 927B' film formed inside the groove after oxidation must reach a certain depth below the surface of the silicon substrate. This amount varies depending on each manufacturing device, but the normal n
Taking the case of Rungis (Channel Recongate MOB) as an example, it is 4ooOAIi! A depth of f is sufficient.

FIG. 2 (roll) shows a silicon dioxide film 27A formed on the surface.

27B' shows a state in which the silicon nitride film 23' and the silicon dioxide film 22' are removed to form an element isolation region after etching down to the surface of the silicon substrate using silicon nitride II23' as an etching-resistant mask.

According to the present invention, a bird's beak is not deformed when manufacturing a semiconductor device with an element isolation structure, and the device region obtained by the above process has no constriction and the surface is flat. In addition, the device surface is flat, and by increasing the depth of the groove, it is possible to separate devices with the same separation width even in a deep diffusion layer that spreads in the depth direction, making it suitable for highly integrated semiconductor devices. This has the effect that nine elements can be separated.

[Brief explanation of drawings]

Figure 1-), Cb), (bite), (d),
(.) is a schematic cross-sectional view of a semiconductor device O1 manufacturing process that performs element isolation by using a conventionally known selective oxidation method, 2nd ml (a) e (b)
-(e), (d), (e) -(f), (g)
-(h) is a schematic sectional view showing the process of Example 01 of the present invention. 21: Silicon substrate, 22.22': Silicon dioxide film, 2
5.25”, @Silicone film, 25: Photoresist, 26:
Impurity as channel stopper, 27: silicon dioxide film, 27m silicon dioxide film, 27B, 27B': polycrystalline silicon, 27r: silicon dioxide film, A: groove 0 Fig. 2

Claims (1)

[Claims] (1) Semiconductor substrate 1 [Procedure of forming grooves by K etching, forming a silicon dioxide film by KCVD method, Step 1 of filling the grooves with polycrystalline silicon to make the surface flat; Step 1 of etching away the polycrystalline silicon to below the interface of the silicon dioxide film so as to leave it in the groove, oxidizing the polycrystalline silicon left in the groove to form a semiconductor substrate I [I
In order to form a silicon dioxide film on the IIIilNT stage and to flatten the surface at the same time, a process 1 was carried out to infiltrate the silicon dioxide film on the semiconductor substrate and inspect the silicon dioxide film on the semiconductor substrate surface. 4111 A method for manufacturing a semiconductor device OII.