JPH04370929A - Dry etching method - Google Patents

Abstract

PURPOSE:To improve the controllability of a trench depth. CONSTITUTION:When trenches 7 are formed in a semiconductor substrate 3 by etching, a two-layer mask 5 for etching is formed of an oxide film 1 and a polysilicon film 2 or a two-layer mask comprising an oxide film and an SiN film is formed to detect the end point of the etching. Thereby, the controllability of the trench depth can be improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method, and more particularly to a dry etching technique that improves the control of the etching amount of a trench in a trench processing technique in a VLSI manufacturing process.

0002

[Prior art and problems to be solved by the invention] Conventionally,
In etching techniques in which a trench is formed in a silicon substrate using a resist or oxide film as a mask material using a reactive ion etching system, there is no film to detect the end point in order to stop etching the silicon film at a certain amount. It is necessary to control the amount of etching by managing the etching rate. However, the etching speed of the equipment changes depending on the number of wafers processed and the equipment condition, and even if the etching speed is measured before processing, the etching speed will change during the processing of one lot, making it difficult to precisely control the amount of etching. Have difficulty. Although this can be controlled to some extent by monitoring before processing, it becomes a factor in reducing throughput in mass production factories. As described above, with the miniaturization of LSIs, variations in trench depth cause deterioration of semiconductor characteristics and lead to a decrease in yield. The present invention aims to solve the above-mentioned problems during the manufacturing of VLSIs, and provides an etching method that can process silicon trenches with good control regardless of fluctuations in the etching speed of an etching device. be.

0003

[Means and operations for solving the problem] In order to solve the above problem, an attempt was made to detect the end point. If a film for detecting the end point is provided in advance during trench processing and it becomes possible to detect the end point, highly controllable etching becomes possible. This invention relates to a silicon etching method in which trench processing is performed on a silicon substrate having a mask layer on the upper surface using a reactive ion etching apparatus, and the present invention relates to a two-layer mask structure in which an oxide film and a polysilicon film are sequentially laminated as the mask material. Alternatively, this is an etching method characterized by using a two-layer mask structure formed by sequentially laminating an oxide film and a SiN film, and controlling the amount of trench etching by monitoring the emission intensity of the mask material during etching.

In the dry etching method of the present invention, the first layer is an oxide film, the second layer is etched during etching of a trench, and when the etching of the second layer is completed, the end point can be detected by emission spectrometry. By using a possible film (a polysilicon film in this example), trench processing with high controllability was made possible. If the area to be etched is large and there is little change in the emission spectrum at the end of the second layer mask etching, a different film such as a silicon nitride film can be used to detect the end point based on the emission spectrum unique to the film. Ideally, the film thickness of the second layer mask is such that the etching of the mask ends when a trench of the desired depth is processed, but if the trench is deep and it is difficult to apply a film of the same thickness as the mask material, This can be done by checking how much over-etching is required to form the desired trench after etching the material.

The dry etching method of the present invention is characterized in that a polysilicon film or a silicon nitride film is used as a mask material, and the etching apparatus is monitored by detecting the end point of the mask material to control the etching amount of the trench. This is an etching method. In this invention,
Perform overetching to obtain the desired trench depth. In this case, a pattern area is required that allows the emission spectrum to change sufficiently when detecting the end point. If the pattern area is too small to detect the end point, it is possible to perform etching similar to a polysilicon mask by using a nitride film instead of a polysilicon film as the mask material and detecting the end point using the unique emission spectrum of the nitride film, which is not affected by silicon. becomes.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiments shown in the drawings. Note that the present invention is not limited thereby. FIGS. 1 to 4 show examples of trench etching when a polysilicon film is used as the mask material. First, as shown in Fig. 1, Si with a film thickness d1 of 2000 Å
The film thickness d2 is 4500 Å through the O2 oxide film (1).
A resist (4) having a predetermined shape for trench formation is patterned on a silicon substrate (3) having a polysilicon layer (2). Next, using the resist (4) as a mask, a pattern of a polysilicon film (2) and an oxide film (1), which will be used as a mask when forming a trench, is formed (see FIG. 2). After removing the polysilicon film (2) and oxide film (1) using a reactive ion etching device to expose the silicon substrate (3) in the trench formation region (T), the resist (4) is removed (FIG. 2). reference). Next, a trench (6) is formed in the silicon substrate (3) using a two-layer mask (5). Figure 3
indicates the state of end point detection. At this time, the polysilicon film (2) is removed. Finally, the depth D is 2.
In order to form a trench (7) of 0 μm, over-etching is further performed (see FIG. 4).

[0007]

Effects of the Invention As explained above, by using the present invention, trench processing with good controllability is possible, and ultra-LS
The yield of I was improved.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing the first step of the manufacturing process in an embodiment of the present invention.

FIG. 2 is a configuration explanatory diagram showing the second step of the manufacturing process in the above embodiment.

FIG. 3 is a configuration explanatory diagram showing the third step of the manufacturing process in the above embodiment.

FIG. 4 is a configuration explanatory diagram showing the fourth step of the manufacturing process in the above embodiment.

[Explanation of symbols]

1　Si　O2　film (oxide film) 2 Polysilicon film 3 Si substrate 4 Resist pattern 5. Two-layer mask 6, 7 Trench

Claims (1)

[Claims] 1. In a silicon etching method in which trench processing is performed on a silicon substrate having a mask layer on the upper surface using a reactive ion etching device, the mask material has a two-layer mask structure in which an oxide film and a polysilicon film are sequentially laminated. Alternatively, a dry etching method characterized by using a two-layer mask structure formed by sequentially laminating an oxide film and a SiN film, and controlling the amount of trench etching by monitoring the emission intensity of the mask material during etching.