JPH01120017A - Pattern formation - Google Patents

Abstract

PURPOSE:To minimize position shift of patterns and to enhance integration, by aligning the photomask to be used for the formation of a third pattern in the direction different from the predetermined direction with respect to both a first and second patterns in the first, second and third patterns being in this order formed. CONSTITUTION:A first pattern is formed on a substrate, and a second pattern is then formed on the substrate using a first photomask aligned with respect to the first pattern. Subsequently, a third pattern is formed on the substrate using a second photomask which is aligned in the predetermined direction with respect to said second pattern and is aligned in the direction different from the predetermined direction with respect to said first pattern. For example, when a contact hole 20A for a source of MOS type memory cells is formed, for the alignment of photomasks, the alignment mark of x-axis direction, which is formed by means of the mask for forming a gate pattern, is used as a reference for an x direction. On the other hand, the alignment mark of y direction, which is formed by means of the mask for forming an active region, is used as a reference for a y direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to improvements in pattern forming methods used in manufacturing semiconductor devices and the like.

[Summary of the Invention] The present invention provides a first and second
In the case where the third pattern is sequentially formed, the degree of integration is improved by aligning the photomask used for forming the third pattern in different directions with respect to the first and second patterns. .

[Prior Art] Generally, in manufacturing semiconductor devices and the like, a method of sequentially forming an insulating material pattern, an open pattern, an electrode material pattern, etc. using a photomask or the like is widely adopted.

In such a method, for example, the first, second and third
When sequentially forming patterns on a substrate, the photomasks used to form each of the second and third patterns were typically aligned with respect to the first pattern.

[Problems to be Solved by the Invention] According to the above-mentioned conventional method, the positional relationship of the third pattern with the second pattern is indirectly regulated via the first pattern. The positional deviation with respect to the pattern becomes considerably large. For this reason, in terms of layout, it is necessary to provide a margin in anticipation of such positional deviation, which has the disadvantage of reducing the degree of integration.

[Means for Solving the Problems] An object of the present invention is to improve the degree of integration by minimizing pattern positional deviation.

In the pattern forming method according to the present invention, after forming a first pattern on a substrate, a second pattern is formed using a first photomask aligned with respect to the first pattern, and then a second pattern is formed on the tube 2. Aligned in a predetermined direction (for example, the X direction) with respect to the pattern, and aligned in a direction different from the predetermined direction (for example, the
direction) using the second photomask aligned in the third direction.
It is characterized by forming a pattern of.

[Function] According to the pattern forming method of the present invention, the third pattern has a minimum positional deviation from the second pattern in the X direction, and a minimum positional deviation from the first pattern in the X direction. becomes.

Therefore, the layout margin is smaller than in the past, and the degree of integration can be improved.

[Embodiment] FIG. 1 is for explaining an embodiment in which the present invention is applied to the manufacture of a MOS type ROM, and shows a planar arrangement of MO3 type memory cells. And A-A' in Figure 1
The cross section along the line and the cross section along the line B-B' are shown in Figures 2 and 3, respectively.
As shown in the figure.

The manufacturing process of the MOS type ROM will be described with reference to these figures.

First, the surface of a semiconductor substrate 10 made of P-type silicon or the like is thinly oxidized, and then a silicon nitride film is deposited thereon by a CVD (chemical vapor deposition) method or the like. Then, this silicon nitride film is patterned using a well-known photolithography technique so that a portion corresponding to the desired active region arrangement hole 12A remains.

Next, by performing selective oxidation using the remaining silicon nitride film portion as a mask, a field insulating film 12 made of silicon oxide is formed on the upper surface of the substrate. After this, the silicon nitride film for the mask and the thin silicon oxide film thereunder are removed. As a result, the field insulating film 12 has active region arrangement holes 1
2A is formed.

In addition, when patterning the silicon nitride described above, the process is used to form alignment marks in the X direction and in the X direction at appropriate locations on the substrate.

Next, the semiconductor surface within the active region arrangement hole 12A is oxidized to form a gate insulating film made of silicon oxide. Then, a polysilicon layer is formed on the gate insulating film by a CVD method or the like. Thereafter, the polysilicon layer is patterned by photolithography using a photomask having a desired gate pattern, thereby forming gate electrode layers 14G+ and 14G2 perpendicular to the active region arrangement hole 12A. In this case, the aforementioned X-direction and X-direction marks are used as references for alignment of the photomask.

In addition, when patterning the polysilicon described above,
Using this process, alignment marks in the X direction and in the X direction are formed at appropriate locations on the substrate.

Next, field insulating film 12 and gate electrode layer 14G
+ and 14G2 are used as masks to selectively dope N-type determining impurities such as phosphorus into the substrate, thereby forming an N-type source region 1B and an N-type drain region 180r and 1.
Form 8D2.

Thereafter, an insulating film such as phosphosilicate glass is deposited on the upper surface of the substrate by CVD or the like. Then, a source contact hole 2O is formed in the insulating film 20 by photolithography using a photomask having a desired source contact pattern.
Form A. In this case, when aligning the photomask, use the alignment mark in the X direction made with the gate pattern forming mask as a reference for the X direction, and
Regarding the direction, the y-direction alignment mark made with the active region forming mask is used as a reference. In this way, the contact hole 2OA and the gate electrode layer 14G2
(or 14G+) (see Figure 2) can be minimized, and the amount of deviation between the contact hole 2OA and the side in the X direction of the active area arrangement hole 12A (b) (see Figure 3) can be minimized. can be minimized. Therefore, the distances a and b
The margin on the layout can be reduced in accordance with the decrease in the amount of deviation.

[Effects of the Invention] As described above, according to the present invention, the degree of integration can be increased by reducing the layout margin,
Particularly, if the present invention is applied to a case where a repeated pattern occupies most of a semiconductor chip, such as in a ROM, the chip area can be reduced.

[Brief explanation of the drawing]

FIG. 1 shows an MO3 for explaining one embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA' in FIG. 1, and FIG. 3 is a cross-sectional view taken along line B-B' in FIG. 1. 10... Semiconductor substrate, 12... Field insulating film,
12A...active area arrangement hole, 14G+,
14G2...gate electrode layer, 16...source region,
1801, 18D2... drain region, 20.
...Insulating film, 2OA...contact hole.

Claims (1)

Claims: (a) forming a first pattern on a substrate; (b) a first pattern aligned with respect to the first pattern;
forming a second pattern on the substrate using a photomask; (c) aligned in a predetermined direction with respect to the second pattern and in a direction different from the predetermined direction with respect to the first pattern; forming a third pattern on the substrate using an aligned second photomask.