JPH03105920A - Detecting method of end point of wet etching - Google Patents

Abstract

PURPOSE:To detect the end point of etching by monitoring the temperature of an Si substrate or the holder of the Si substrate when the specified section of the Si substrate is wet-etched. CONSTITUTION:A vessel 2 made of pyrex glass is bonded in a region including the circular window 13 in the rear of an X-ray mask supporter 1. The X-ray mask supporter 1 is placed on a pyrex glass base 5 so as not to be brought into contact with the pattern forming section P on the surface of the X-ray mask supporter 1. A thermocouple 6 is set to one part of a region except the pattern forming section P on the surface of the X-ray mask supporter 1 under a contacted state at that time. The detecting data of the thermocouple 6 are recorded in a recorder 7. Since a temperature change by an exothermic reaction with an etchant 3 during etching remarkably appears in an Si substrate 11, the end point of etching is detected by monitoring the temperature of the supporter 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an end point detection method for detecting the end point of wet etching processing.

(Prior Art) FIGS. 3(a) and 3(b) are cross-sectional views for explaining the process of etching in the production of an X-ray mouse, in which 11 is a silicon (Si) substrate, 12 is an X-ray The permeable membrane 13 is a window of the permeable membrane 2, and 14 is an absorber pattern.

Generally, a method for completely removing a predetermined portion of the Si substrate l1 by wet etching is used for manufacturing a silicon sensor or for X4! The X-ray mask shown in FIG. 3(b) is obtained by wet etching the Si substrate 11 at the window 13 in FIG. 3(a).

FIG. 4 is a sectional view showing a conventional wet etching apparatus, in which 15 is the xi mask support shown in FIG. 3(a), 16 is
is a container made of glass etc. that contains etching solution,
(2) 7 is an O-shaped ring, 18 is an etching table, 19 is an etching solution, and 20 is a heater.

In the figure, first, the window l on the back side of the X-ray mask support 15 is
3 and place the container 16 on top of it. At this time, an O-shaped ring 17 is used to shield the etching solution 19 from seeping out from the contact area between the container 16 and the X-ray mask support 15 during etching. When using the 0-shaped ring 17, the container 16 and the X-ray mask support 15 are tightened and fixed using a jig so that there is no gap in the contact area between the two.

Next, the X-ray mask support 15 is set on the etching table 18 on which the four parts 113a are formed so that the pattern forming portions P on the surface of the X-ray mask support 15 do not come into contact with each other. After this, etching solution 19 is put into container 16 to perform etching. As the etching solution 19, a mixed solution of fluoronitric acid and acetic acid or an aqueous solution of KOH is used.

When selecting the etching liquid 19, it is necessary to use a liquid in which the X-ray transmitting film 12 of the xg mask support 15 is not etched by the etching liquid 19. A mixed solution of fluoronitric acid and acetic acid has a fast etching rate and can be etched at room temperature. X
Etching of the X-ray mask support 15 proceeds by oxidizing the X-ray mask support 15 with nitric acid and removing the oxide film with hydrofluoric acid.

Therefore, as the etching progresses, the absolute amount of nitric acid decreases, the reaction rate decreases, and the etching solution must be replaced frequently.

In etching using a KOH aqueous solution, the etching rate is determined by the KOH concentration and solution temperature.

For this reason, it is necessary to heat the KOH aqueous solution.

As a method of heating the etching solution, the X-ray mask support 15
There is a method of heating the etching solution and a method of directly heating the etching solution using a heater or infrared heating. FIG. 4 shows an example in which a KOH aqueous solution is used as the etching solution and heated using the heater 20.

When a KOH aqueous solution is used as the etching solution, the KOH aqueous solution reacts with the Si substrate 11 and is dissolved in the etching solution in the form of Si oxide or Si hydroxide, and the reaction progresses. Hydrogen gas is generated when producing Si oxide or Si hydroxide. A large amount of bubbles due to hydrogen gas are generated in the KOH aqueous solution. During etching, water in the KOH aqueous solution evaporates rapidly, so
Need to refill water. The completion of etching is determined by the amount of bubbles in the KOH aqueous solution.

Further, when a mixed solution of hydrofluoric nitric acid and acetic acid is used as the etching solution, the Si substrate 11 is oxidized by the nitric acid to become silicon oxide, and then the silicon oxide is etched by the hydrofluoric acid.

This reaction is exothermic and generates a large amount of heat, heating the X-ray mask support 15. Also, a large amount of nitrogen dioxide gas is generated by the reaction. The end of etching is determined visually when nitrogen dioxide gas is no longer generated.

(Problems to be Solved by the Invention) In the above-mentioned conventional technique, in etching using a KOH aqueous solution as the etching solution 19, completion of etching is determined by visually observing disappearance of bubbles in the KOH aqueous solution.

Therefore, if etching progresses non-uniformly, a residue remains. Also, the side surface of the Si substrate 11 which is the material to be etched is
Since bubbles are generated even after the radiation transmitting film 12 is left, there is a problem that it is difficult to detect the end point of etching.

In addition, etching using a mixture of fluoro-nitric acid and acetic acid
Etching is terminated when nitrogen oxide gas is no longer generated.

However, similar to the case of using the KOH aqueous solution described above, there are problems such as residues remaining and etching progressing on the sidewalls of the Si substrate 11.

An object of the present invention is to provide a method for detecting the end point of wet etching that can accurately determine the end point of etching.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for wet etching a predetermined portion of an Sj substrate.
A feature of this method is that the end point of etching is detected by monitoring the temperature of the i-substrate holder.

(Function) Since the above method is adopted, the temperature of the Si substrate significantly changes due to the exothermic reaction with the etching solution during etching. Therefore, by monitoring the temperature of the Si substrate or the holder of the Si substrate, the etching An end point is detected.

(Example) Embodiments of the present invention will be described below based on the drawings.

Fig. 3 is a cross-sectional view showing an apparatus for carrying out an embodiment of the method for detecting the end point of wet etching according to the present invention, and 1 is an X-ray mask support having the structure shown in Fig. 3(a). ,
2 is a container in which etching solution 3 is stored, 4 is adhesive grease, 5 is a glass stand, 6 is a thermocouple, 7 is a recorder, 8
is a heater.

X-ray mask support 1 was manufactured by the following method. That is,
To explain with reference to FIG. 3(a), 3-inch Si
X is formed on the substrate 11 using the LPCVD method (low pressure chemical vapor deposition method).
The SiN film of the radiation transmitter film 12 is deposited to a thickness of 2-. After forming a circular resistor pattern of 40 rrmφ on the back surface of the Si substrate 1l, the SiN film in the circular portion of 40 mmφ is removed by RIE (reactive ion etching) using SF and gas to form the window 13. To run away.

Then, tungsten, which is the material for the absorber pattern 14, is sputter deposited onto the surface of the Si substrate 11.

The film thickness is 0.6-. Thereafter, an electron beam resist is applied and baked, and a predetermined pattern is exposed by electron beam exposure, and then developed. Finally, the tungsten is etched using the electron beam resist as a mask using the RIE method to form the X-ray mask support 1.

In FIG. 1, 40 nm of the back surface of the X-ray mask support 1
In an area of 50nwφ including the circular window 13 of φ, an inner diameter of 50
A Pyrec glass container 2 having a diameter of 5 mm, an inner thickness of 5 mm, and a height of 50 m is glued. At this time, in order to bond the X-ray mask support stand 1 and the container 2 together, grease 4 is applied between them.

Next, x, vh The pattern shape or part P on the surface of the mask support ↓
Place the X-ray mask support l on a Pyrec glass stand 5 so that it does not come in contact with the X-ray mask support l. At this time, a thermocouple 6 is attached to a part of the surface of the X-ray mask support other than the patterned part P.
set so that they are in contact. The detection data of this thermocouple 6 is recorded on a recorder 7.

The heater 8 is heated by 1 φ to prevent it from being corroded by the etching solution 3.
The stainless steel cylinder is filled with nichrome wire as a heater material and magnesium oxide as an insulator.

Further, the voltage applied to the heater is 65V, 1. LA was used, and a 14N-KOH aqueous solution was used as the etching solution.

FIG. 2 is an explanatory diagram showing the relationship between etching time and temperature, and the temperature decrease during the etching process is due to K.
This is because water was replenished because the OH aqueous solution evaporated. Replenishment of KOH aqueous solution is approximately 30cc every 60 minutes. The liquid temperature instantly drops to about 50°C, but rises to 60°C in about 10 minutes. The part where the temperature decreases after etching exceeds 4 hours (arrow in the figure) is the end point of etching, and thereafter the temperature is maintained at 55°C.

Even when etching is performed with a mixture of fluoro-nitric acid and acetic acid,
The liquid temperature increases and similar temperature characteristics are observed.

Further, the side surface of the Si substrate 11 on the side to be etched continues to be etched even after the etching in the film thickness direction is completed. Therefore, no matter which etching solution is used,
Although the generation of bubbles and gas is observed, the amount remains constant even after the etching is completed, so the temperature remains constant after the etching is completed.

Note that even if the shape of the Si substrate 11 is such that it is attached to a holder such as a reinforcing frame, the temperature can be measured on the front surface of the Si substrate l1 or the back surface of the holder such as a reinforcing material in the same manner as in the above embodiment. You can know the end point of etching.

(Effects of the Invention) According to the present invention, it is possible to provide a method for detecting the end point of wet etching that can accurately determine the end point of etching by monitoring the temperature of the Si substrate or the holder for the Si substrate.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an apparatus for carrying out an embodiment of the wet enoching end point detection method according to the present invention;
The figure is an explanatory diagram showing the relationship between etching time and temperature.
FIGS. (a) and (b) are cross-sectional views for explaining the wet etching process, and FIG. 4 is a cross-sectional view showing a conventional wet etching apparatus. 1. X-ray mask support, 2. Container, 3.
Etching solution, 4... Grease, 5... Glass stand, 6... Thermocouple, 7... Recorder,
8... Heater.

Claims (1)

[Claims] A method for detecting the end point of wet etching, characterized in that when wet etching a predetermined portion of a silicon substrate, the end point of etching is detected by monitoring the temperature of the silicon substrate or a holder for the silicon substrate.