JP2723598B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of forming grooves having different depths.

2. Description of the Related Art In a manufacturing process of a semiconductor device, it is necessary to dig a trench in order to form a trench for element isolation, a trench capacitor in a DRAM, and the like. By the way, depending on the product, it may be necessary to form grooves of a plurality of depths. Such an example will be described with reference to FIG. 3 and FIG.

FIG. 3 is a cross-sectional view of a transistor portion of the bipolar integrated circuit. As shown in FIG.
An N ⁺ type buried layer 12 and an N ⁻ type epitaxial layer 13 are formed on 11. A collector lead region 14 and a base region 15 are formed in the N ⁻ type epitaxial layer 13, and a base lead region 16 and an emitter region 17 are further formed in the base region 15. An insulating film 18 is provided on the semiconductor substrate, and an Al electrode that is in contact with the semiconductor region via a contact hole formed in the insulating film is formed on the insulating film 18. In this semiconductor device, a deep trench 20 for separating a transistor from other regions and a shallow trench 21 between a base region 15 and a collector lead-out region for preventing lateral diffusion of both regions are formed.

FIG. 4 is a sectional view of the MOS integrated circuit. As shown in FIG. 4, an N well 32 and a P well 33 are formed in a P type semiconductor substrate 31, and a P channel is formed in the N well 32. A MOSFET 34 is formed. In this example, the N well 32 and the P well 33 are separated by the deep trench 20 to reduce the leak current between them.
Further, the shallow trench 21 separates the MOSFETs 34, and suppresses the occurrence of a parasitic PNP transistor therebetween.

Conventionally, as means for forming such a plurality of types of grooves, those shown in FIGS. 5 and 6 have been known. Hereinafter, a conventional manufacturing method will be described with reference to these drawings.

In the first manufacturing method, as shown in FIG. 5, a film 42 is formed on a semiconductor substrate 41 using a material having a large etching selectivity as a substrate material, and a photoresist 43 having a first pattern is formed thereon. [FIG. 5 (a)]. The first pattern-shaped deep groove 44 is formed by using an anisotropic etching method.
Is formed, and the photoresist 43 is removed [FIG. 5 (b)]. After filling the inside of the groove 44 with a filler to form a deep trench 45, the film 42 is removed, and a similar film 42a is newly formed.
And a photoresist having a second pattern thereon
43a is formed [FIG. 5 (c)]. A shallow groove 46 having a second pattern shape is formed, the photoresist 43a is removed, and from FIG. 5 (d), the inside of the shallow groove 46 is filled with a filler to form a second groove.
A shallow trench 47 having the above pattern shape is formed [FIG. 5 (e)].

The second conventional example is shown in FIG. 6, in which a photoresist 43b of a second pattern is formed on a film 42 (FIG. 6 (a)), a shallow groove 46 is formed, and then a first pattern is formed. (FIG. 6B). Subsequently, a deep groove 44 is formed, the photoresist 43c is removed, and the grooves 44 and 46 are filled with a filler to form a deep trench 45 and a shallow trench 47 [FIG. 6 (c)]. Figure (d)].

[Problems to be Solved by the Invention] Among the above-mentioned conventional methods, the first method involves forming a deep trench and a shallow trench in separate steps, so that the number of steps is large and the manufacturing time is one. It takes about twice as much time as when manufacturing a trench. As a result, the wafer is easily contaminated and the chance of being damaged is increased, and it is difficult to improve the yield.

On the other hand, in the second method, when the photo-resist 43c is removed, a part of the photo-resist 43 tends to remain in the shallow groove 46 as a residual resist 48, which is a source of contamination and lowers the yield. Further, since etching is performed twice at the portions where the grooves shown in FIG. 6 (e) intersect, FIG. 6 (f) which is a cross-sectional view taken along the line XX ′ of FIG. The groove becomes too deep as shown. For this reason, when filling the inside of the groove, it may not be possible to fill the groove sufficiently, and there is a fear that a disconnection accident may occur when the wiring passes therethrough.

Furthermore, since both the first and second conventional methods form two types of grooves using different mask patterns, a margin for mask alignment is required, which is an obstacle to high density. .

[Means for Solving the Problems] In the method of manufacturing a semiconductor device according to the present invention, a first depth groove having a first pattern shape and a second depth having a second pattern shape are formed in a semiconductor substrate. Forming a film on the semiconductor substrate using a material capable of forming a mask at the time of etching the semiconductor substrate; and selectively etching the film. Forming a first pattern and a second pattern exposing the semiconductor substrate surface, and exposing the first pattern and its peripheral portion with a margin with respect to the first pattern, Forming a mask pattern covering the second pattern and the peripheral portion thereof; and etching the mask using the mask pattern and the film as a mask to form the first pattern shape. Forming a groove from the surface of the semiconductor substrate to a desired depth, removing the mask pattern and etching using the film as a mask, forming a groove having a first depth of the first pattern shape on the semiconductor substrate; Forming a groove having a second depth of the second pattern shape.

[Example] Next, an example of the present invention will be described with reference to the drawings.

1 (a) to 1 (c) are cross-sectional views of a semiconductor device showing process steps of one embodiment of the present invention.

First, as shown in FIG. 1A, when a semiconductor substrate is etched on a semiconductor substrate 1, the semiconductor substrate material (Si) has a large etching selectivity, that is, a mask used when etching the semiconductor substrate. A film 2 is formed using a material capable of forming a film, and then a photoresist 3 is applied, and a first pattern 5 and a second pattern 6 are formed on the photoresist 3 and the film 2 by a photolithography technique. I do.

Next, as shown in FIG. 1 (b), the photoresist 3 is removed, and the second photolithography technique is used again.
The photoresist 4 is formed so as to cover the pattern of FIG. Next, the semiconductor substrate 1 is subjected to anisotropic etching using the photoresist 4 and the film 2 as a mask to form a first groove 8a.

Subsequently, as shown in FIG.
Is removed, and again using the film 2 as a mask, the semiconductor substrate 1
Is anisotropically etched to form a first groove 8 and a second groove 9 at the same time.

In the steps after FIG. 1 (c), after oxidizing the sidewalls of the trenches or forming a nitride film on the sidewalls, the interiors of the trenches 8 and 9 are made of polysilicon, oxide using TEOS or BPSG, If the above-mentioned material is deposited under the condition that the deep groove is sufficiently filled, and then etched back until the substrate surface is exposed, a deep trench and a shallow trench can be simultaneously formed.

In this manufacturing method, when performing anisotropic etching using CCl ₄ or CBrF ₃ as an etching gas for silicon,
Since the etching selectivity of silicon to the silicon oxide film and the silicon nitride film is 30 and 10, respectively, it is desirable to use a silicon oxide film, a silicon nitride film, or a composite film thereof as the material of the film 2.

In the above-described embodiment, the steps which are increased compared to the case where only one type of groove 8 is formed are only the step of forming the photoresist 4 and the step of removing the same. On the other hand, the conventional first method requires two separate trench manufacturing steps, so that the method of the embodiment can reduce the number of steps and the manufacturing time to approximately half of the first method. it can.
The fact that the number of steps and the manufacturing time can be reduced by half means that the chance of receiving contamination or damage is reduced by half, so that the yield can be significantly improved according to the present invention.

Also, according to the method of this embodiment, two types of grooves having different depths can be formed at the same time, and it is not necessary to protect the previously formed groove with a photoresist.
An accident that the photoresist remains in the groove as in the conventional example does not occur. However, in the step shown in FIG. 1B, there is no possibility that the photoresist remains in the groove 8a in the step of forming the photoresist 4, but since the photoresist in this portion is an unexposed portion, the photoresist developing step Can be almost completely removed. Also,
Even if a part remains, it is removed in the subsequent etching step, so that it does not become a contamination source. Since the grooves are not formed unnecessarily deep as shown in FIG. 6 (f) at the intersections of the grooves, the grooves can be buried flat and the wiring formed thereon can be disconnected. Absent. Further, since the first and second patterns are formed using the same mask, the alignment margin required in the conventional method becomes unnecessary, and the density can be increased.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, first, second, and third patterns are formed by the photoresist 3 (FIG. 2A).
After that, a photoresist 4 is formed to form a groove 8a.
FIG. (B)] Next, the groove 8 is formed using the photoresist 4a as a mask.
b and 9a are formed [FIG. 2 (c)].
By removing a, grooves 8, 9, and 10 are formed. In this embodiment, a positive type material is used as the material of the photoresist 4, and the photoresist 4 may be exposed again to form the pattern 4a. First
According to the conventional method described above, forming three types of grooves requires about three times as many man-hours and time as forming one type of groove. On the other hand, in this embodiment, Since it is only necessary to add the steps of forming and removing the photoresists 4 and 4a to the step of forming one kind of groove, the effect of reducing the number of steps is further increased.

[Effects of the Invention] As described above, according to the present invention, when grooves having different depths are formed in a semiconductor substrate, a film is formed on the substrate using a material having a large etching selectivity with silicon, and this film is formed. According to the present invention, the first and second patterns are formed first, a groove is first formed halfway in the first pattern shape, and then the etching is continued in the first and second pattern shapes. Since two types of grooves can be formed at the same time and the inside of the grooves can be filled at the same time, the number of steps for manufacturing the semiconductor device can be reduced, and the manufacturing period can be shortened. And, by shortening the manufacturing process, the probability of adhesion of dust, contamination, generation of scratches, etc. is reduced, and the yield can be improved.

Further, since a deep groove and a shallow groove can be formed at the same time, a resist or the like does not remain in the groove, thereby preventing contamination. Further, since the intersection between the deep groove and the shallow groove does not become unnecessarily deep, the intersection is not filled completely.
Further, according to the present invention, since the position of the pattern of the deep groove and the shallow groove is determined by one alignment exposure, an alignment margin is not required, and a high-density integrated circuit can be realized. Further, even when three or more types of grooves having different depths are formed, the grooves can be easily formed by adding a small number of steps (for example, adding an exposure / development and an etching step).

[Brief description of the drawings]

1 (a) to 1 (c) and 2 (a) to 2 (d) are cross-sectional views of a semiconductor device showing a process sequence of an embodiment of the present invention, and FIGS. FIGS. 5 (a) to 5 (e) and FIGS. 6 (a) to 6 (d) are cross-sectional views of a semiconductor device to be manufactured according to the present invention, showing a process sequence of a conventional example. , FIG. 6 (e) shows FIGS.
A plan view of a semiconductor device manufactured by the step (d);
FIG. 6 (f) is a sectional view taken along the line XX 'of FIG. 6 (e). 1, 41 ... semiconductor substrate, 2, 42 ... film, 3, 4, 4a, 43, 43a to 43c ... photoresist, 5 ... first pattern, 6 ... second pattern, 7 ... Pattern 3, 8, 8a, 8b First groove 9, 9a Second groove 10, Third groove 11, P-type semiconductor substrate 12, N ⁺ buried layer , 13 …… N ^- type epitaxial layer, 14
…… Collector extraction area, 15… Base area, 16 …… Base extraction area, 17 …… Emitter area, 18 …… Insulating film, 19 …… Al electrode, 20 …… Deep trench, 21 …… Shallow trench, 31 ... P-type semiconductor substrate, 32 ... N well, 33 ... P well, 34 ... MOSFET, 44 ... deep trench, 45 ... deep trench, 46 ... shallow trench, 47 ... shallow trench, 48 ... ... resist remaining.

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising: forming a first depth groove having a first pattern shape and a second depth groove having a second pattern shape in a semiconductor substrate. A step of forming a film on a substrate using a material capable of forming a mask at the time of etching the semiconductor substrate; and a first pattern in which the film is selectively etched to expose the semiconductor substrate surface. Forming a second pattern, exposing the first pattern and its peripheral portion with a margin with respect to the first pattern, and forming a mask pattern covering the second pattern and its peripheral portion; Forming a groove in the first pattern shape from the surface of the semiconductor substrate to a desired depth by performing etching using the mask pattern and the film as a mask Removing the mask pattern and performing etching using the film as a mask to form a groove having a first depth of the first pattern shape and a groove having a second depth of the second pattern shape on the semiconductor substrate. And a method of manufacturing a semiconductor device.