JPH0432227A - Method for detecting end point in dry etching and method for forming contact hole using it - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an end point detection method for determining the timing of the end point of etching of a specific layer to be removed by etching in a dry etching process of an MO8 type semiconductor device, and this end point detection method. The present invention relates to a contact hole forming method in which a contact hole is formed using a contact hole.

Conventional technology The end point detection method used in conventional dry etching processes accurately detects the timing when etching has progressed to the interface between a specific layer to be etched and a layer below this specific layer that will not be etched. There were difficulties in detecting it.

As shown in FIG. 4(b), a part of the insulating layer 3 formed on the P-type silicon substrate 1 is removed by dry etching, and the n1 diffusion layer 2 formed on the P-type silicon substrate 1 is removed.
When forming the contact hole 8 that reaches the end point, the end point is conventionally detected as follows. Here, as a specific layer, 11 layer 3 oak'):I oxide film (th-3iO□, LPCVD-3i02゜APC
VD-3iOt). At the start of dry etching, a photoresist 4 is formed on the insulating layer 3 corresponding to the location where the contact hole 8 is to be formed, as shown in FIG. 4(a). CHF5 for etching. A gas such as Os is used, and the 00 emission spectrum [-carbon oxide emission spectrum] is measured during etching, and the end point time is determined based on the change in the intensity of this 00 emission spectrum. Specifically, the amount of oxygen generated from the silicon oxide film as the insulating layer 3 during etching is reduced when the insulating layer 3 is completely removed. Conventionally, this change in the amount of oxygen generated is determined from a decrease in the 00 emission spectrum.

Problem to be Solved by the Invention As shown in FIG. 2(a), the change in the 00 emission spectrum is not sensitive to the reduction of oxygen generated from the silicon oxide film as the insulating layer 3, but is due to the etching of the silicon oxide film. It is often difficult to determine the end point.

Since the end point is not detected accurately in this manner, there is a problem that ion energy is incident on the n+ diffusion layer 2 of the impurity diffusion layer, causing etching damage and increasing the contact resistance value. Although it is conceivable to reduce the etching damage by slowing down the etching speed, this is not preferable because it reduces the throughput.

The present invention provides an end point detection method that can accurately detect the etching end point of a specific layer to be removed by etching, and a contact hole that uses this end point detection method to avoid occurrence of etching damage and realize a low contact resistance value. The purpose is to provide a method for forming.

Means for Solving the Problems A method for detecting an end point in dry etching according to claim 1 includes forming a silicon nitride film in advance under a specific layer to be dry etched, and removing the silicon nitride film from the silicon nitride film during dry etching. 3. The contact hole forming method according to claim 2, further comprising measuring a generated CN emission spectrum to determine whether or not the etching of the specific layer is complete. When forming a contact hole by etching, a silicon nitride film is formed in advance under the insulating layer corresponding to the location where the contact hole is to be formed, and the CN emission spectrum generated from the silicon nitride film is measured during dry etching. 4. The method of forming a contact hole according to claim 3, further comprising detecting the end of etching the layer, and changing etching conditions to etch the silicon nitride film after detecting the end of etching the insulating layer. The etching conditions in claim 2 are changed by performing etching under etching conditions that give priority to etching speed and etching uniformity until the end of etching of the insulating layer is detected, and after detecting the end of etching of the insulating layer. The method is characterized in that the silicon nitride film is etched by changing the etching conditions to conditions that can suppress the ion energy incident on the impurity diffusion layer formed on the semiconductor substrate.

According to the structure of claim 1, since a silicon nitride film is formed in advance under a specific layer to be dry etched, it is possible to measure the CN emission spectrum generated from the silicon nitride film during dry etching. Therefore, it can be determined that the etching of the specific layer has been completed at the time when the emission intensity suddenly increases.

According to the structure of claim 2.3, when forming a contact hole, an end point indicating the end of etching of the insulating layer is detected, and the etching conditions of the semiconductor device before and after that are switched, so that the throughput and etching can be improved. It can improve the damage problem.

EXAMPLES The end point detection method of the present invention will be explained below based on specific examples. Here, C will be explained using an example in which a hole is formed. Components having the same functions as those in FIG. 4 showing the conventional example will be described with the same reference numerals.

In FIG. 1(a), a P-type silicon (100) substrate l
Form an n+ diffusion layer 2 on the top layer with a film thickness of 50 nm.
A silicon thermal oxide film 5 is formed. Furthermore, a silicon nitride film 6 with a thickness of 50 nm is formed on the upper layer by low pressure CVD, and as an interlayer insulating film, a film with a thickness of 8Q is formed by normal pressure CVD.
Onm's B P S G (Bolori Phosp
A thin Silica Glass film 7 is formed respectively. Finally, a photoresist 4 having a thickness of 1 to 2 um is formed after patterning contact holes.

The silicon nitride film 6 is formed to monitor that the BPSG film 7 has been removed by increasing the CN (carbon nitride) emission spectrum, and the silicon thermal oxide film 5 directly oxidizes the silicon nitride film 6. This is to prevent defects occurring in the P-type silicon substrate 1 by forming it on the P-type silicon substrate 1.

First, using the photoresist 4 as a mask, the BPSG film 7 is
RI E (Reactive ton Etchi
ng) Etch into a vertical shape (Fig. 1(b)
). Etching conditions at this time include, for example, CHF5
Gas 30 sccm, 02 gas 3 sec, He gas 15 sec, vacuum degree 20 Pa, SRF power 500 W
shall be. The above etching conditions are etching conditions that give priority to etching speed and etching uniformity, and the energy of ions incident on the P-type silicon substrate l is 500%.
The etching conditions are quite large, on the order of eV.

When the BPSG film 7 is removed and the silicon nitride film 6 is exposed, the 00 emission spectrum decreases as shown in FIG. 2(a), and the CN emission spectrum increases as shown in FIG. 2(b). However, as is clear from Figure 2, the decrease in the emission spectrum of CHF.

It is weak due to the use of gas such as 02,
It is difficult to stably determine the end point of etching the BPSG film 7. On the other hand, the increase in the CN emission spectrum was remarkable, and the end point of etching of the BPSG film 7 was reached at time t. It is possible to make stable judgments. In addition, as shown in Figure 2 (C), the difference between the amount of light emitted by CN and the amount of light emitted by CO is also shown, and by taking this difference, it is possible to more stably determine the end point of etching. Let me add something.

After the silicon nitride film 6 is exposed 2 (before the impurity diffusion layer is exposed), the etching conditions are changed to suppress the ion energy of the ions incident on the substrate, and the impurity diffusion layer is etched as shown in FIG. 1(C). A contact hole 8 reaching the n'''' diffusion layer 2 is formed. Etching conditions at this time include, for example, CHF3 gas 30 sec, 02
Gas 3 sccm, He gas 15 sec, vacuum degree 2
0 Pa and RF power of 250 W. The above etching conditions reduce the RF power by half compared to the first etching condition, and the etching speed and etching uniformity may deteriorate, or the energy of ions incident on the P-type silicon substrate 1 may be around 250 eV. This is reduced by half compared to the etching conditions of No. 1. The etching conditions are to reduce the number of ions implanted into the impurity diffusion layer or to reduce the contact resistance value.

FIG. 3 is a graph comparing the contact resistance values when the final etching is performed under the first etching condition and when the "-force distribution method" is applied. It can be seen that by halving the energy of ions incident on the P-type silicon substrate 1, it is possible to approximately halve the contact resistance value.

In this way, the BP of the insulating film as a specific layer to be removed by etching corresponds to the location where the contact hole 8 is to be formed.
Since the silicon nitride film 6 is formed under the SG film 7,
By measuring the CN emission spectrum generated from this silicon nitride film 6, the end point of etching of the BPSG film 7 can be accurately determined. Furthermore, since the etching conditions are switched after this end point, good contact holes can be made efficiently.

In the above embodiment, the detection of the end point of an insulating layer in a contact hole forming method was used as an example, or it was used to determine when to finish etching a specific layer to be removed in manufacturing processes other than contact hole formation. You can also do that.

As described above, according to the end point detection method according to claim 1,
A silicon nitride film is formed in advance under a specific layer to be dry etched, and the CN emission spectrum generated from the silicon nitride film is measured during dry etching to determine whether etching of the specific layer is complete. The etching end point of a specific layer can be detected more accurately than before.

In addition, in the contact hole forming method according to claim 2.3, when forming a contact hole by dry etching the insulating layer formed on the semiconductor substrate, the insulating layer is etched under the insulating layer corresponding to the contact hole forming location. A silicon nitride film is formed in advance, and the end of etching of the insulating layer is detected by measuring the CN emission spectrum generated from the silicon nitride film during dry etching, and after detecting the end of etching of the insulating layer. Since the silicon nitride film is etched by changing the etching conditions, the insulating layer can be etched quickly and uniformly, improving productivity in forming contact holes. Furthermore, it is possible to reduce the ion energy incident on the impurity diffusion layer provided in the semiconductor substrate and located at the final end of the contact hole, reducing etching damage to the impurity diffusion layer and lowering the contact resistance value. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the contact hole forming process, FIG. 2 is an emission spectrum diagram during dry etching, FIG. 3 is an explanatory diagram comparing the contact resistance reduction results according to an embodiment of the present invention, and FIG. FIG. 3 is a cross-sectional view of a conventional contact hole forming process. ■...P-type silicon substrate [semiconductor substrate], 2...n
'''Diffusion layer, 6... Silicon nitride film, 7... BPS
G film (insulating layer), 8... contact hole. Agent Yoshihiro Morimoto Figure 1, Figure 1, Time opening diagram (Funtakt side A) -' (p.

Claims (1)

[Claims] 1. A silicon nitride film is formed in advance under a specific layer to be dry etched, and the CN emission spectrum generated from the silicon nitride film is measured during dry etching to determine the characteristics of the characteristic layer. A method for detecting the end point in dry etching to determine the end of etching. 2. When forming contact holes by dry etching the insulating layer formed on the semiconductor substrate, a silicon nitride film is formed in advance under the insulating layer corresponding to the location where the contact hole is to be formed, and then dry etching is performed. CN emission spectrum generated from the silicon nitride film is measured to detect completion of etching of the insulating layer, and after detecting completion of etching of the insulating layer, etching conditions are changed to etch the silicon nitride film. Hole formation method. 3. When forming contact holes by dry etching the insulating layer formed on the semiconductor substrate, a silicon nitride film is formed in advance under the insulating layer corresponding to the location where the contact hole is to be formed, and then dry etching is performed. Etching is performed under etching conditions that give priority to etching speed and etching uniformity until the completion of etching of the insulating layer is detected by measuring the CN emission spectrum generated from the silicon nitride film. After detecting the contact hole, the silicon nitride film is etched by changing the etching conditions to conditions that can suppress the ion energy incident on the impurity diffusion layer formed on the semiconductor substrate.