JP2964635B2 - Method for manufacturing semiconductor memory device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a MOS nonvolatile semiconductor memory device, and more particularly, to a method for manufacturing a MOS nonvolatile semiconductor memory device having a floating gate electrode.

[Conventional technology]

2. Description of the Related Art Conventionally, in this type of manufacturing method of a MOS type nonvolatile semiconductor device, as shown in FIG. 2, a thermal oxide film having a thickness of, for example, 300 to 1000 mm is formed as an insulating film 2 on a semiconductor substrate 1 (see FIG. (FIG. 2 (a)), a part of the insulating film 2 and a part of the semiconductor substrate 1 in a predetermined region are sequentially removed by using a known photolithography technique to form a groove (FIG. 2 (b)), and the photoresist 4 is formed. After the removal, an oxide film is formed as a buried insulating film 5 by, for example, a chemical vapor deposition method in an amount of 10,000 to 20,000, and
The embedded insulating film 5 is reflowed and flattened by performing a heat treatment at about 0 ° C. to 1000 ° C. (FIG. 2C), and the entire surface is etched back until the semiconductor substrate 1 is exposed. A thermal oxide film of about 500 ° is formed (FIG. 2 (d)), and a first polycrystalline silicon film 8 containing impurities, for example, phosphorus is formed on the entire surface (FIG. 2 (e)). The first polycrystalline silicon film 8 in a predetermined region is removed by a lithography technique (FIG. 2F), and after removing the photoresist 9, a second polycrystalline silicon film is formed on the first polycrystalline silicon film.
A thermal oxide film of, for example, 200.degree. To 1000.degree. Is formed as the insulating film 10, and a step of forming a second polycrystalline silicon film 11 containing impurities, for example, phosphorus (FIG. 2 (g)).

[Problems to be solved by the invention]

The conventional method of manufacturing a MOS nonvolatile semiconductor memory device described above uses a photolithography technique when patterning the first polycrystalline silicon film 8 as shown in FIG. There are two problems.

Since the separation width L1 of the first polycrystalline silicon film is determined by the photolithography technology, it cannot be smaller than the minimum separation width by the photolithography technology.

Since the separation of the first polycrystalline silicon film is performed by the photolithography technique, misalignment occurs. For this reason, a margin must be provided for misalignment, and L2 must be increased.

As a result, the element isolation width L3 becomes large due to the above two problems, and the MOS nonvolatile semiconductor memory device becomes large.

[Means for solving the problem]

A method of manufacturing a MOS nonvolatile semiconductor memory device according to the present invention includes the steps of sequentially forming an insulating film and a polycrystalline silicon film on a semiconductor substrate; and forming a polycrystalline silicon film in a predetermined region using a known photolithography technique. Forming a groove in the semiconductor substrate by removing the insulating film and part of the semiconductor substrate, forming a first buried insulating film having a film thickness that does not completely fill the entire surface of the semiconductor substrate, A step of forming a second insulating film having a thickness to be buried, a step of etching back the entire surface until the surface of the first buried insulating film is exposed, and a step of forming the first buried insulating film until the surface of the polycrystalline silicon film is exposed. A step of selectively etching back the film, a step of sequentially removing the polycrystalline silicon film and the insulating film on the entire surface to form a gate insulating film, and a step of forming a first polycrystalline silicon film containing impurities on the entire surface And the whole A step of forming a planarizing material to planarize the surface and then etching back the entire surface until the second buried insulating film is exposed; and a step of removing a planarizing material to remove a second planarizing material on the first polycrystalline silicon film. Forming a second polycrystalline silicon film containing an undesired substance on the entire surface, or after sequentially forming the insulating film and the polycrystalline silicon film on the semiconductor substrate. Forming a first insulating film, and removing a part of the first insulating film, the polycrystalline silicon film, the insulating film, and the semiconductor substrate in a predetermined region using a known photolithography technique to form a semiconductor substrate. A step of forming a groove, a step of forming a first buried insulating film having a film thickness that does not entirely fill the groove, a step of forming a second insulating film having a film thickness that completely fills the groove over the entire surface, 1 until the surface of the buried insulating film is exposed. Etch-back, selectively etching back the first buried insulating film and the first insulating film until the surface of the polycrystalline silicon film is exposed, and sequentially removing the entire surface of the polycrystalline silicon film and the insulating film. Removing, forming a gate insulating film, forming a first polycrystalline silicon film containing impurities on the entire surface, forming a planarizing material on the entire surface, planarizing the surface, and then forming a second buried layer. A step of etching back the entire surface until the insulating film is exposed; and a step of forming a second insulating film on the first polycrystalline silicon film after removing the planarizing material and then including a second polycrystalline silicon containing impurities on the entire surface. A step of forming a film, or a step of sequentially forming a gate insulating film and a polycrystalline silicon film containing impurities on a semiconductor substrate, and a step of forming a predetermined region using a known photolithography technique. Many Forming a groove in the semiconductor substrate by removing a portion of the crystalline silicon film, the insulating film, and the semiconductor substrate; forming a first buried insulating film having a film thickness that does not completely fill the groove on the entire surface; Forming a second insulating film having a thickness that fills all the grooves;
Etching back the entire surface until the surface of the buried insulating film is exposed, and the first step until the surface of the polycrystalline silicon film is exposed.
Selectively etching back the buried insulating film, forming a first polycrystalline silicon film containing impurities on the entire surface, forming a planarizing material on the entire surface, and planarizing the surface. A step of etching back the entire surface until the buried insulating film 2 is exposed, and forming a second insulating film on the first polycrystalline silicon film after removing the planarizing material, and a second step including impurities on the entire surface. Having a step of forming a polycrystalline silicon film, or forming a first insulating film after sequentially forming a gate insulating film and a polycrystalline silicon film containing impurities on a semiconductor substrate; Forming a groove in the semiconductor substrate by removing a part of the first insulating film, the polycrystalline silicon film, the gate insulating film and the semiconductor substrate in a predetermined region by using a known photolithography technique; Is all buried Forming a first buried insulating film having a thickness not exceeding the thickness of the first insulating film;
Etching back the entire surface until the surface of the buried insulating film is exposed, and the first step until the surface of the polycrystalline silicon film is exposed.
Selectively etching back the buried insulating film and the first insulating film, forming a first polycrystalline silicon film containing impurities on the entire surface, and forming a planarizing material on the entire surface to form a surface. After planarization, a step of etching back the entire surface until the second buried insulating film is exposed, and after removing the planarizing material, forming a second insulating film on the first polycrystalline silicon film and forming an impurity on the entire surface. Forming a second polycrystalline silicon film containing

〔Example〕

Next, the present invention will be described with reference to the drawings. First
The figure is a longitudinal sectional view of one embodiment of the present invention. First, the insulating film 2 is formed on the semiconductor substrate 1 by, for example, thermal oxidation to form a film 200 to 1000.
Is formed, and a polycrystalline silicon film 3 is formed thereon by, for example, a chemical vapor deposition method to a thickness of 1000 to 4000 (FIG. 1A).
Using a known photolithography technique, a part of the polycrystalline silicon film 3, the insulating film 2, and a part of the semiconductor substrate 1 in a predetermined region is sequentially etched and removed to form a groove (FIG. 1B).
A first buried insulating film 5 is formed on the entire surface by, for example, an oxide film having a thickness of 1000Å10000Å by a chemical vapor deposition method. Then, the second buried insulating film 6 is etched back until the surface of the first buried insulating film 5 is exposed, and then the first buried insulating film 5 is removed. The polycrystalline silicon film 3 is selectively etched with, for example, hydrofluoric acid until the surface of the polycrystalline silicon film 3 is exposed (FIG. 1 (d)).
Is formed by, for example, a thermal oxidation method (FIG. 1 (e)), and a first polycrystalline silicon film containing impurities, for example, phosphorus is formed on the entire surface by, for example, a chemical vapor deposition method to have a thickness of 1000 to 60 °.
Then, a photoresist 9 is formed on the entire surface as a planarizing material.
Is formed and the surface is flattened (FIG. 1 (f)), the entire surface is etched back until the surface of the second buried insulating film 6 is exposed, and the first polycrystalline silicon film 8 is buried in the second buried insulating film 6. Insulating film 6
(FIG. 1 (g)), and after removing the photoresist 9, a second insulating film 10 is formed on the first polycrystalline silicon film 8 by, for example, a thermal oxidation method at 100 to 1000 °. A second polycrystalline silicon film 11 containing an impurity, for example, phosphorus is formed by, for example, a chemical vapor deposition method at 1000 to 6000.degree. (FIG. 1 (h)).

In another method of manufacturing the above-mentioned MOS type nonvolatile semiconductor memory device, as shown in FIG. 3, first, an insulating film 2 is formed on a semiconductor substrate 1 by a thermal oxidation method for 200 to 1000 Å. Is formed, and a polycrystalline silicon film 3 is formed thereon by, for example, a chemical vapor deposition method.
And 4000Å is formed, the oxide film of the first insulating film 12 and to, for example, chemical vapor deposition on the film thickness d ₂ is formed (FIG. 3 (a)), a predetermined region using a known photolithography technique The first insulating film 12, the polycrystalline silicon film 3, the insulating film 2, and a part of the semiconductor substrate 1 are sequentially etched to form a groove (FIG. 3B), and a first buried insulating film is formed on the entire surface. The oxide film is formed in a thickness of 1000 to 10000 by a chemical vapor deposition method, for example.
Then, a second buried insulating film 6 is formed on the entire surface by, for example, a chemical vapor deposition method to form a nitride film of 1,000 to 10,000 Å (FIG. 3C), and the second buried insulating film 6 is formed on the entire surface. First
Etch back until the surface of the buried insulating film 5 is exposed,
Subsequently, the first buried insulating film 5 and the first insulating film 12 are selectively etched with, for example, hydrofluoric acid until the surface of the polycrystalline silicon film 3 is exposed (FIG. 3D). As a result, the height of the protruding portion of the second buried insulating film 6 is d ₁ + d ₂ , which is smaller than d ₁ , which has a limitation that the film thickness is less than half of L 3.
of the amount corresponding to d ₂ can be high, also not fundamentally limited to the d _2.
Subsequently, the subsequent steps are exactly the same as those shown in FIGS. 1 (e) to 1 (h), and will not be described.

In another method for manufacturing the above-mentioned MOS type nonvolatile semiconductor memory device, as shown in FIG. 4, first, a gate insulating film 7 is formed on a semiconductor substrate 1 by, for example, a thermal oxidation method.
A polycrystalline silicon film 3 having a thickness of 100 to 1000 ° and containing impurities such as phosphorus is formed thereon by, for example, chemical vapor deposition.
The polycrystalline silicon film is formed in a predetermined area by using a known photolithography technique.
3. A groove is formed by sequentially etching and removing a part of the gate insulating film 7 and the semiconductor substrate 1 (FIG. 4 (b)), and the first
The buried insulating film 5 is formed, for example, by an oxide film of 1000-10000 ° by the chemical vapor deposition method, and then the second buried insulating film 6 is formed on the entire surface by the nitride film of 1000 例 え ば by the chemical vapor deposition method.
.About.10000.degree. (FIG. 4 (c)), the second buried insulating film 6 on the entire surface is etched back until the surface of the first buried insulating film 5 is exposed, and then the first buried insulating film 5 is formed. Is selectively etched with, eg, hydrofluoric acid until the surface of the polycrystalline silicon film 3 is exposed (FIG. 4 (d)), and a first polycrystalline silicon film containing impurities, eg, phosphorus, is chemically The surface is planarized by forming a photoresist 9 as a planarizing material on the entire surface (FIG. 4E), and the surface of the second buried insulating film 6 is exposed on the entire surface. Then, the first polycrystalline silicon film 8 is separated by the width L1 of the second buried insulating film 6 (FIG. 4F), and after removing the photoresist 9, the first polycrystalline silicon film 8 is removed. A second insulating film 10 is formed on the silicon film 8 by, for example, a thermal oxidation method to a thickness of 100 to 1000. By the second polycrystalline silicon film 11 containing phosphorus if example, for example, chemical vapor deposition
A thickness of 1000 to 6000 is formed (FIG. 4 (g)).

As another method, after replacing the insulating film 2 with the gate insulating film 7 in FIG. 3 and performing FIGS. 3 (a) to 3 (d), FIG. 4 (g) can also be performed.

〔The invention's effect〕

As described above, according to the present invention, the first polycrystalline silicon film is separated by using the second buried insulating film having a width smaller than the width of the groove buried in the groove, without using the photolithography technique. The following effects are obtained because the backing is performed.

The separation width of the first polycrystalline silicon film can be made smaller than the separation limit of the photolithography technique.

The isolation of the first polycrystalline silicon film can be formed in a self-aligned manner with respect to the element isolation groove.

That is, the width L3 of the element isolation groove shown in FIG.
2 × L2 can be reduced until it becomes the same as the minimum separation width of the photolithography technology.

In addition, since the cross-sectional shape of the first polycrystalline silicon film after separation is concave, the area facing the second polycrystalline silicon film is increased, and the capacitance value can be increased. Can be written and erased faster than before (FIG. 5).

[Brief description of the drawings]

1 (a) to 1 (h) are longitudinal sectional views of one embodiment of the present invention. 2 (a) to 2 (g) are longitudinal sectional views of a conventional example. 3 (a) to 3 (d) are longitudinal sectional views of a second embodiment of the present invention. 4 (a) to 4 (g) are longitudinal sectional views of a third embodiment of the present invention. FIG. 5 is a view showing the characteristic improvement effect of the present invention. DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Insulating film, 3 ... Polycrystalline silicon film, 4,9 ... Photoresist, 5 ... First buried insulating film, 6 ... Second buried insulating film, 7 ... ... Gate insulating film, 8 first polycrystalline silicon film, 10 second insulating film, 11 second polycrystalline silicon film, 12 first insulating film.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/8247 H01L 27/115 H01L 29/788 H01L 29/792

Claims (4)

(57) [Claims] In a MOS nonvolatile semiconductor memory device having a floating gate electrode, a step of sequentially forming an insulating film and a polycrystalline silicon film on a semiconductor substrate, and a step of forming a predetermined region using a known photolithography technique. Forming a groove in the semiconductor substrate by removing a part of the polycrystalline silicon film, the insulating film and the semiconductor substrate, and forming a first buried insulating film having a film thickness that does not completely fill the groove on the entire surface. Forming, forming a second insulating film on the entire surface to a thickness that fills the entire groove, etching back the entire surface until the surface of the first buried insulating film is exposed, Selectively etching back the first buried insulating film until the surface of the silicon film is exposed; forming a gate insulating film by sequentially removing the polycrystalline silicon film and the insulating film from the entire surface; A step of forming a first polycrystalline silicon film containing impurities and a step of forming a planarizing material on the entire surface to planarize the surface and then etching back the entire surface until the second buried insulating film is exposed; Removing the planarizing material, forming a second layer on the first polycrystalline silicon film.
Forming an insulating film and forming a second polycrystalline silicon film containing impurities on the entire surface.
A method for manufacturing an S-type nonvolatile semiconductor memory device. A step of forming a first insulating film after forming an insulating film and a polycrystalline silicon film on the semiconductor substrate in sequence, and a step of forming the first insulating film in a predetermined region using a known photolithography technique. Forming a groove in the semiconductor substrate by removing the film, the polycrystalline silicon film, the insulating film, and a part of the semiconductor substrate, and a first buried insulating film having a thickness that does not completely fill the groove on the entire surface. Forming a second insulating film having a thickness that completely fills the groove on the entire surface; etching back the entire surface until the surface of the first buried insulating film is exposed; 2. The manufacturing method of a MOS nonvolatile semiconductor memory device according to claim 1, further comprising a step of selectively etching back the first buried insulating film and the first insulating film until the surface of the silicon film is exposed. Method. 3. In a MOS nonvolatile semiconductor memory device having a floating gate electrode, in particular, a step of sequentially forming a gate insulating film and a polycrystalline silicon film containing impurities on a semiconductor substrate; Forming a groove in the semiconductor substrate by removing a part of the polycrystalline silicon film and the insulating film and the semiconductor substrate in a predetermined region by using a technique; A step of forming a first buried insulating film, a step of forming a second insulating film having a thickness that completely fills the trenches on the entire surface, and etching back the entire surface until the surface of the first buried insulating film is exposed Performing a step of selectively etching back the first buried insulating film until the surface of the polycrystalline silicon film is exposed; and forming a first polycrystalline silicon film containing impurities on the entire surface. Forming a planarizing material on the entire surface and planarizing the surface, and then etching back the entire surface until the second buried insulating film is exposed; and removing the planarizing material and removing the first polycrystalline material. Forming a second insulating film on the silicon film and forming a second polycrystalline silicon film containing impurities on the entire surface thereof. 4. A step of forming a first insulating film after sequentially forming a gate insulating film and a polycrystalline silicon film containing impurities on a semiconductor substrate, and forming a first insulating film in a predetermined region by using a known photolithography technique. Forming a groove in the semiconductor substrate by removing the first insulating film, the polycrystalline silicon film, the insulating film, and a part of the semiconductor substrate; A step of forming a buried insulating film, a step of forming a second insulating film having a thickness that completely fills the entire groove, and a step of etching back the entire surface until the surface of the first buried insulating film is exposed 4. The MOS nonvolatile semiconductor device according to claim 3, further comprising a step of selectively etching back the first buried insulating film and the first insulating film until the surface of the polycrystalline silicon film is exposed. Semiconductor memory device Production method.