JPH07245291A - Method and apparatus for etching silicon substrate - Google Patents

Abstract

PURPOSE:To provide a method and an apparatus for etching silicon substrates wherein etch rate for silicon substrates is controlled with accuracy, and wherein harmful effect, such as variations, on the performance of products is prevented. CONSTITUTION:Before etching a silicon substrate 1 (6), a monitor film 2 is formed using a silicon material different from that of the silicon substrate 1 (for example, poly-Si or amorphous Si is used if the substrate to be etched is of Si). The monitor film is etched together with the substrate. Thus the degree of etching to the monitor film is monitored by means of emission spectrum or the like, and the etch rate for the substrate is thereby controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon substrate etching method and etching apparatus. INDUSTRIAL APPLICABILITY The present invention can be used as an etching technique for a silicon-based substrate in various fields such as semiconductor device manufacturing. In the present specification, "silicon-based" means that the main constituent atoms such as silicon, polysilicon, and amorphous silicon are Si.
What is.

[0002]

2. Description of the Related Art Conventionally, silicon-based substrates have been etched in various situations. For example, when a silicon semiconductor device is manufactured, the LOCOS region, trench isolation, trench capacitor, and connection holes such as via holes and contact holes are formed in the Si substrate, so that the substrate is etched or bonded. SOI
Even when the structure is formed, a step is formed on the Si substrate by etching.

However, in the prior art, the etching amount was controlled only by the etching time. Therefore, if there are variations in the etching rate,
This was a direct variation in the amount of etching.

The above-mentioned problems of the prior art will be described in more detail with reference to FIG. Here, as one of methods for forming an insulating film for element isolation, a problem of the above-described conventional technique will be described by taking a technique of digging a groove in the Si substrate 1 and then filling the groove with an oxide film as an example.

Referring to FIG. In this conventional technique, the following steps are taken. The P-type Si substrate 1 is oxidized to deposit a pad SiO ₂ film 3 of 20 nm, for example. Then, a Si ₃ N ₄ film 4 (for example, 150 nm) is formed on this by C
Deposit using the VD method.

Next, as shown in FIG. 8B, after etching off the Si ₃ N ₄ film 4 and the SiO ₂ film 3 in the portion forming the element isolation region by the RIE method using the resist 7 as a mask, the remaining parts remain. The Si substrate 1 is etched by 200 nm, for example, using the Si ₃ N ₄ film 4 / SiO ₂ film 3 as a mask.

In the prior art, the etching amount here is controlled by controlling the etching time.

After the above etching, as shown in FIG. 8C, the substrate wafer is placed in a high temperature steam atmosphere of about 950 ° C. to oxidize Si and grow a SiO ₂ film (500 nm, for example). L as the element isolation region 9
An OCOS region is formed.

The above conventional technique has the following problems. That is, since the control of the etching amount of the Si substrate 1 depends only on the time, there is a problem that the etching amount itself varies when there is fluctuation in the etching rate. This variation in the etching amount directly affects the processing conditions of the upper gate poly-Si layer, the isolation characteristics of the narrow channel transistor characteristics in the active transistor region surrounded by the element isolation region, and the like.
Very problematic.

[0010]

SUMMARY OF THE INVENTION As described above, in the prior art,
Since the etching amount of the silicon-based substrate is controlled by the etching time, there is a problem that the etching amount of the substrate to be etched cannot be accurately controlled.

The present invention solves this problem and provides an etching method and etching apparatus for a silicon-based substrate which can accurately control the etching amount of the silicon-based substrate and prevent variations in product performance and other adverse effects. It is intended to be provided.

[0012]

The invention according to claim 1 of the present application is an etching method for etching a silicon-based substrate, wherein a monitor film is formed of a silicon-based material different from the material of the silicon-based substrate to be etched, A method for etching a silicon-based substrate, wherein the etching amount of the silicon-based substrate to be etched is controlled by simultaneously etching the silicon-based substrate to be etched and the monitor film to monitor the degree of etching of the monitor film. Therefore, the above object is achieved thereby.

The invention of claim 2 of the present application is characterized in that the etching end point of the silicon substrate to be etched is removed at the time when the monitor film is removed by etching. The above etching method achieves the above object.

The invention according to claim 3 of the present application is characterized in that the silicon substrate to be etched is a silicon substrate and the monitor film is formed of polysilicon or amorphous silicon. A method for etching a silicon-based substrate as described above, which achieves the above object.

According to a fourth aspect of the present invention, the etching is etching of a substrate for forming an insulating portion for element isolation, and the silicon-based substrate according to any one of the first to third aspects. An etching method which achieves the above object.

The invention of claim 5 of the present application is characterized in that the etching is etching of a substrate for forming a trench capacitor or a connection hole.
The method for etching a silicon-based substrate according to any one of 1 to 3, which achieves the above object.

According to a sixth aspect of the present invention, in an etching apparatus for etching a silicon-based substrate, the material to be etched is on a silicon-based substrate to be etched, and a silicon-based material different from the material of the silicon-based substrate to be etched is used. A silicon-based substrate etching apparatus comprising a monitor film formed of a material, and a monitor means for detecting an emission spectrum of the monitor film during etching, which achieves the above object. To do.

[0018]

According to the etching method of the present invention, at the time of etching, different kinds of silicon-based monitor films formed on the silicon-to-be-etched substrate are simultaneously etched to monitor the degree of etching of the monitor film. Since the etching amount of the substrate is controlled (for example, the etching end point of the silicon substrate to be etched is set at the time when the monitor film is removed by etching), proper etching control can be achieved and a predetermined etching without variation can be realized. In this case, since the monitor film is made of a silicon-based material, it has a property similar to that of the substrate to be etched and is used for a convention in a semiconductor process, so that it can be realized conveniently and advantageously. For example, the substrate to be etched and the monitor film may be appropriately selected from silicon, polysilicon, amorphous silicon, or the like and combined.

According to the etching apparatus of the present invention, since the emission spectrum at the time of etching the monitor film is monitored,
It is possible to perform reliable monitoring with a simple structure, and thus it is possible to realize proper etching without variations.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. However, it should be understood that the present invention is not limited to the embodiments.

Example 1 This example is an application of the present invention to etching of a Si substrate for forming an insulating film for element isolation in a Si semiconductor device manufacturing process.

First, the outline of this embodiment will be described with reference to FIGS.

In this embodiment, in the etching method for etching a silicon substrate, the monitor film 2 is made of a silicon material (here, polysilicon) different from the material of the silicon substrate 1 (here, the silicon substrate) to be etched.
(FIGS. 1 and 2), the silicon substrate 1 to be etched and the monitor film 3 are simultaneously etched (FIG. 3),
The etching amount of the silicon substrate 1 to be etched is controlled by monitoring the degree of etching of the monitor film 2 (FIGS. 4 and 5).

In particular, in this embodiment, a proper etching end point is detected by setting the etching end point of the silicon substrate 1 to be etched when the monitor film 2 is removed by etching.

Further, the etching apparatus of this embodiment is shown in FIG.
As shown in FIG. 5, the monitor means 8 for monitoring the emission spectrum 21 from the monitor film 2 on the substrate 1 to be etched is provided.

The specific structure of the embodiment will be described in more detail below.

In this embodiment, in the technique of forming a trench in the silicon substrate 1 for forming an insulating film for element isolation and then filling the trench with an oxide film, the etching technique of the present invention is applied to the formation of the trench. It is a thing.

As shown in FIG. 1, the P-type Si substrate 1 is oxidized to deposit a pad SiO ₂ film 3 (20 nm). Then, on this, Si ₃ N ₄ film 4 (150 nm)
Are deposited using the CVD method. Furthermore, on this film Si
The O ₂ film 5 (100 nm) is deposited by the CVD method. After that, a polysilicon film (200 nm) having the same thickness as the etching depth of the Si substrate 1 is deposited by the CVD method in the subsequent step to form the monitor film 2.

Next, as shown in FIG. 2, a portion of the polysilicon film (monitor film 2) / SiO in which an element isolation region is formed is formed.
_{The 2} film 5 / Si ₃ N ₄ film 4 / pad SiO ₂ film 3 is etched by RIE using the patterned resist 7 as a mask.

Next, after removing the resist mask, the polysilicon film (monitor film 2) and the silicon substrate 1 are simultaneously etched as shown in FIG. 3 to etch the silicon substrate 1 by 20 nm. The etching is schematically indicated by arrow 6. The etching at this time has a selectivity of about 10 or more with respect to SiO ₂ .

Here, the etching amount of the polysilicon film as the monitor film 2 is monitored by monitoring the emission spectrum 21 of SiF, SiCl or the like to detect the degree of etching (see FIG. 7). This monitor can be easily performed because the intensity of the emission spectrum or the like decreases (the etching area and amount decrease) when the monitor film 3 (polysilicon) (200 nm) in the active region is etched. If the etching rate of the polysilicon forming the monitor film 2 is different from that of the silicon substrate which is the substrate to be etched, the monitor film 2 to be deposited in anticipation thereof
The film thickness of the (polysilicon film) may be adjusted.

FIG. 4 shows the state after etching. Figure 4
The reference numeral 3 ′ indicates the portion where the monitor film 3 is etched (etching off portion), and the reference numeral 11 indicates the portion where the silicon substrate 1 is etched (etching off portion).

Next, as shown in FIG. 5, a Si ₃ N ₄ film 4 is formed.
The upper SiO ₂ film 5 is removed by the RIE method. The removed portion (etching-off portion) is indicated by reference numeral 5 '. This etching has a selectivity of about 10 or more with respect to Si ₃ N ₄ 5 and Si.

Further, by placing the substrate wafer 1 in a water vapor atmosphere, silicon is oxidized to grow a SiO ₂ film (500 nm) forming a LOCOS region which is an element isolation region 9.

According to this embodiment, it is possible to accurately control the etching amount of silicon. Further, as a result, when applied to the formation of an insulating film for element isolation, it becomes possible to improve the controllability of the element isolation characteristic and the controllability of the active element characteristic surrounded by the element isolation region. It was

Example 2 In this example, as in Example 1, the present invention was applied to the etching of a groove for forming a trench capacitor. As a result, it was possible to form a good trench capacitor with no variation in capacity.

Example 3 In this example, as in Example 1, the present invention was applied to the etching of a groove for forming trench isolation. As a result, similar to Example 1, it was possible to form good trench isolation with no variation in element isolation characteristics.

Example 4 In this example, similarly to Example 1, the present invention was applied to the etching of the groove for forming the connection hole. As a result, a good groove having no variation can be formed, and a good connection structure having no variation can be realized.

Examples 5 to 8 In the above Examples 1 to 4, the monitor film 2 was changed from polysilicon to amorphous silicon, and the other processes were performed in the same manner. As a result, a similar effect could be obtained.

[0040]

According to the present invention, there is provided an etching method and an etching apparatus for a silicon-based substrate which can accurately control the etching amount of the silicon-based substrate and prevent variations and other adverse effects on the production of products. I was able to.

[Brief description of drawings]

FIG. 1 is an example showing the steps of Example 1 in order of cross-sectional views (1).

FIG. 2 is an example showing the steps of Example 1 in order of cross-sectional views (2).

FIG. 3 is an example showing the steps of Example 1 in order of cross-sectional views (3).

FIG. 4 is an example showing the steps of Example 1 in order of cross-sectional views (4).

FIG. 5 is an example showing the steps of Example 1 in order in sectional views (5).

FIG. 6 is an example showing the steps of Example 1 in order in cross-sectional views (6).

FIG. 7 is a configuration diagram of an etching apparatus according to a first embodiment.

FIG. 8 is a diagram showing a conventional technique.

[Explanation of symbols]

1 silicon substrate to be etched (Si substrate) 2 monitor film (polysilicon, amorphous silicon) 3 SiO ₂ 4 Si ₃ N ₄ 5 SiO ₂ 6 etching 7 resist 8 monitoring means 9 element isolation region (LOCOS) 21 emission spectrum

Claims (6)

[Claims] 1. An etching method for etching a silicon substrate, wherein a monitor film is formed of a silicon material different from the material of the silicon substrate to be etched, and the silicon substrate to be etched and the monitor film are simultaneously etched. A method for etching a silicon-based substrate, wherein the etching amount of the silicon-based substrate to be etched is controlled by monitoring the degree of etching of the monitor film. 2. The method for etching a silicon-based substrate according to claim 1, wherein the etching end point of the silicon-based substrate to be etched is removed when the monitor film is removed by etching. 3. The method for etching a silicon-based substrate according to claim 1, wherein the silicon-based substrate to be etched is a silicon substrate and the monitor film is formed of polysilicon or amorphous silicon. . 4. The etching according to claim 1, wherein the etching is etching of a substrate for forming an insulating portion for element isolation.
4. The method for etching a silicon-based substrate according to any one of 3 to 3. 5. The method of etching a silicon-based substrate according to claim 1, wherein the etching is etching of a substrate for forming a trench capacitor or a connection hole. 6. An etching apparatus for etching a silicon-based substrate, wherein the material to be etched is on the silicon-based substrate to be etched.
A monitor film is formed of a silicon material different from the material of the silicon substrate to be etched, and a monitor means for detecting an emission spectrum of the monitor film during etching is provided. Substrate etching equipment.