JPH04245433A - Simulation method of etching process - Google Patents

Abstract

PURPOSE:To simulate the etching operation of many layers by a method wherein an etching rate for other substances, to be etched, which have been exposed by deleting a point train is applied to the substances and a point train is moved by an etching rate which is peculiar to each substance. CONSTITUTION:An oxide film 2 is formed on a silicon substrate 1; a nitride film 3 is formed on the oxide film 2. When a developed resist 4 exists on its upper part, a point train 5 is formed around each substance. An etching operation is made to progress clockwise; the intersection P of a point train is detected at each time step. At a stage where the intersection of the point train 5 has been detected, the point train is cut into pieces; a substance to be etched on the lower layer is exposed. Regarding a face (a flag is given as a candidate of a point to be moved to a point train included in the face) which comes into contact with an etching substance, an etching operation is continued at an etching rate which is decided by each substance to be etched and the etching substance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process simulation method in a multilayer etching process.

0002

2. Description of the Related Art In the conventional etching simulation method, only a single layer etching simulation was performed. This is, for example, ``PROCEEDINGS OF
THE IEEE)” Vol. 71, No. I, J
Annual, 1983, the paper “Icy Process Modeling and Topography Design”
IC Process Modeling an
d Topography Design). In this etching simulation method, as shown in FIG. 4, an oxide film 2, a nitride film 3, and a resist 4 are placed on a silicon substrate 1 as the materials to be etched, and the regions in contact with the etching material (ionic hydrochloric acid, etc.) are Point sequence 5
will be established. As shown in FIG. 5(a), this point sequence 5 calculates the etching distance obtained from the product of the etching direction A obtained from the bisector angle B between the three point sequences 5, the etching time, and the etching rate for each point. A new point sequence 5 is obtained by moving each point by the etching distance in that direction.

A flowchart in this case is shown in FIG. First, in step 11a, the area in contact with the etching substance is rotated clockwise as shown in FIG.
2,...,i,N). Next, in step 12, the exposed point sequence 5 is moved by a vector Ri, which is the product of the vector Vi and the etching time Δt. Furthermore, it is determined in step 21 whether or not this dot sequence has entered another etching target material, and if so, the dot sequence 5 that has entered another etching material is deleted in step 22. This operation is continued until the end of the etching time in step 18.

0004

[Problems to be Solved by the Invention] The conventional etching simulation method described above can only perform etching simulation of a single layer. Or even if it reached the silicon substrate, it could not be determined that it was a foreign substance. Therefore, when attempting to perform a multilayer etching simulation, there is a drawback that etching continues at the same etching rate.

An object of the present invention is to provide an etching process simulation method that can solve these problems and perform multilayer etching simulation.

[0006]

[Means for Solving the Problems] The structure of the etching simulation method of the present invention is such that in the step of providing a dot array around each of all the materials to be etched and etching from the top of the material to be etched, It is determined whether the etching has reached the material to be etched by sequentially detecting the intersections of the dot rows, the intersecting dot rows are deleted, and the previously continuous dot row is divided into multiple points. The method is characterized in that the etching rate of the substance exposed by the deletion of the dot sequence is applied to other substances to be etched, and the dot sequence is moved according to the etching rate unique to each substance.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flowchart illustrating an embodiment of the present invention. First, as shown in step 11, each of the same material layers is surrounded by a clockwise series of points. For the exposed point sequence, as in step 12, as shown in FIG. 5(a)
Similarly, in the etching direction A, the etching time Δt
The vector Ri of the etching distance, which is found by the product of the vector Vi of the etching speed
)), move each point. At this time, step 13,1
4, determine whether the line segments formed by the point sequence 5 intersect,
If they intersect (step 15), then in step 16 that part is divided into one point sequence, and in step 1
7, among the newly generated point sequences, those that are counterclockwise are deleted (see FIG. 2(b)). As a result, etching can be continued except for the dot rows that affect other layers. The above steps are repeated until the etching time ends (step 18).

FIGS. 3(a) to 3(d) are cross-sectional views for explaining this embodiment. First, as shown in FIG. 3(a), an oxide film (SiO2) 2 is placed on a silicon substrate 1, a nitride film (Si3N4) 3 is placed on this oxide film 2, and a developed film is placed on top of the nitride film (Si3N4). Assume that there is a resist 4 that is Next, as shown in FIG. 3(b), a dot array 5 is provided around each substance. Etching is performed in the same manner as shown in FIG. 5, and the intersection P of the dot sequence is detected at each time step Δt.

When the intersection P of the dot array 5 is detected, the dot array is divided to expose the underlying material to be etched as shown in FIG. 3(c), and the etched material is etched as shown in FIG. Then, continue etching on the surface that is in contact with the etching material (a flag is given to the series of points included in this surface as candidates for moving points) at the etching rate determined by each etching material and the etching material. I will do it. Thereafter, by performing etching according to the flow shown in FIG. 1, it becomes possible to perform a multilayer simulation similar to actual etching.

0010

[Effects of the Invention] As explained above, the present invention can perform multilayer etching simulation, so by setting the same settings as those used for actual microfabrication of integrated circuits, it is possible to optimize the etching time and etching process. This has the effect of allowing the selection of materials to be determined in advance.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an etching simulation process according to an embodiment of the present invention;

FIGS. 2(a) and 2(b) are a coordinate diagram of an intersection point P and a schematic cross-sectional view illustrating the deletion of a point sequence in the process of this example;

FIGS. 3(a) to 3(d) are cross-sectional views showing this example in the order of etching steps;

FIG. 4 is a cross-sectional view showing a conventional etching simulation process;

FIG. 5 is a coordinate diagram illustrating the direction of etching in FIG. 4 and a schematic diagram of an etching region;

[Fig. 6] Flowchart of conventional etching simulation process,

[Explanation of symbols]

1 Silicon substrate 2 Oxide film 3 Nitride film 4 Resist 5 point sequence A Etching direction B Bisector angle

Claims (2)

[Claims] [Claim 1] In the step of providing a dot array around each of all the etching target materials and etching from the top of the etching target materials, it is sequentially determined whether or not the etching has reached other adjacent etching target materials. The judgment is made by detecting the intersection of point sequences, the intersecting point sequence is deleted, the previously continuous point sequence is divided into multiple point sequences, and other objects exposed by the deletion of the point sequence are A method for simulating an etching process, characterized in that an etching rate of the material is applied to the etching material, and a series of dots is moved according to the etching rate unique to each material. [Claim 2] Intersection of a series of points is the intersection of a linear equation expressing one line segment between points with a linear equation expressing another line segment on which line segment. Claim 1 determined by
A simulation method of the described etching process.