JPH03179445A - Thin ceramic film - Google Patents

Abstract

PURPOSE:To prevent a shift of a focus when a ceramic coated substrate is used as a photomask by specifying the thickness of a ceramic film formed on one side of a silicon substrate of a specified thickness and forming a ceramic film having the same quality on the other side by chemical vapor deposition in a specified thickness. CONSTITUTION:A ringlike silicon substrate 11 is coated with at least one of silicon carbide and silicon nitride by chemical vapor deposition to form a ceramic film 12. The pref. thickness of the substrate 11 is 100-1,000mum. The ceramic film 12A formed on one side of the substrate 11 is 0.1-20mum and the ceramic film 12B formed on the other side is made 0.85-1.15 times as thick as the film 12A. The curving of the silicon substrate due to the difference between the coefft. of thermal expansion of the substrate and that of the ceramic film is inhibited, the flatness of the substrate can be ensured and a shift of a focus can be inhibited when the ceramic coated substrate is used as a photomask at the time of drawing an electronic circuit on a semiconductor wafer.

Description

[Detailed Description of the Invention] (1) Purpose of the Invention [Field of Industrial Application] - Concerning a ceramic thin film used as a photomask when drawing a dovetail lightning circuit. In particular, a ceramic film of the same quality (i.e., at least one of silicon carbide and silicon nitride) as the front surface is also deposited on the back surface of the silicon substrate by chemical vapor deposition.
This relates to a ceramic thin film formed to double the film thickness.

[Prior Art] Conventionally, this type of ceramic thin film is produced by forming a ceramic film by coating at least one of silicon carbide and silicon nitride on one mirror-finished surface (i.e., the surface) of a silicon substrate by chemical vapor deposition. In order to use the ceramic film as a ceramic thin film, it has been proposed to remove a part of the silicon substrate by etching from the other side (ie, the back side).

[Problems to be Solved] However, with conventional ceramic thin films, it is difficult to form a ceramic film by coating at least one of silicon carbide and silicon nitride only on the surface of a silicon substrate.
However, due to the difference between the coefficient of thermal expansion of the ceramic thin film and the coefficient of thermal expansion of the ceramic film, the flatness of the ceramic thin film is affected due to the curvature that occurs in the silicon substrate during the cooling process after chemical vapor deposition. Furthermore, (11) when a ceramic thin film is used as a photomask for drawing electronic circuits on a semiconductor wafer using X-cotton, there is a drawback that the focus is out of focus. there were.

Therefore, in order to eliminate these drawbacks, the present invention aims to provide a ceramic thin film in which a ceramic film of the same quality as the front surface is formed also on the back surface of a silicon substrate.

(2) Structure of the Invention (c) Solution to Problem 1 The solution to the problem provided by this research is to coat one surface of a silicon substrate with at least one of silicon carbide and silicon nitride by chemical vapor deposition. In the ceramic thin film created by later removing a part of the silicon substrate by etching from the other side, the thickness of the silicon substrate is 100 to 11,000 μ, and the thickness of the coating on one side of the silicon substrate is 0.5 μm. 1 to 20 μm, and the other surface of the silicon substrate is coated with a coating of the same quality as one surface by chemical vapor deposition to a thickness of 0.85 to 1.15 times. .

[Operation 1] As specified in [Means for solving problems], the ceramic thin film according to the present invention coats one surface of a silicon substrate with at least one of silicon carbide and silicon nitride by chemical vapor deposition, and then coats a part of the silicon substrate with at least one of silicon carbide and silicon nitride. It is a ceramic thin film created by removing the silicon substrate from the other side by etching process, and is particularly suitable for silicon substrates with a thickness of 100 to 1
1000u, and the thickness of the ceramic film formed by coating on one side of the silicon substrate is 0.1~
20 μm, and a ceramic film of the same quality as the first surface is formed by chemical vapor deposition on the other surface of the silicon substrate to a thickness of 0.85 to 1.15 times. This has the effect of suppressing the bending of the silicon substrate due to the difference between the coefficient of thermal expansion of the ceramic film and the thermal expansion coefficient of the ceramic film. When used as a photomask for drawing circuits, it acts to suppress the occurrence of focal shifts.

[Example] Next, the ceramic thin film according to the present invention will be described in detail by giving preferred examples thereof with reference to the accompanying drawings.

FIG. 1 is a plan view showing a first embodiment of a ceramic thin film according to the present invention, in which the central portion of a silicon substrate 11 is removed by etching. It shows the case.

FIG. 2 is a sectional view taken along line II-II Im of the embodiment in FIG.

FIG. 3 is a plan view showing a second embodiment of the ceramic thin film according to the present invention, in which the central portion and some edge portions of the silicon substrate 11 are removed by etching. ing.

FIG. 4 is a sectional view taken along the line IV--IV of the embodiment of FIG.

FIG. 5 (al to ffl are cross-sectional views for explaining the manufacturing method of the embodiment in FIG. 1 and the embodiment in FIG. 3;
When manufacturing the ceramic thin film of the example in Figure 3, a cross-sectional view along the line ■-■ is shown, and when manufacturing the ceramic thin film of the example in Figure 3, a cross-sectional view along the line ■-v is shown. There is.

First, the structure of a first embodiment of the ceramic thin film according to the present invention will be described in detail with reference to FIGS. 1 and 2.

The ear is a ceramic thin film according to the present invention, and has a negative surface (
IIA (also called the front side) and the other side (also called the back side)
IIB are both mirror-finished and a part (in this case, the center part; FIG. A ceramic II formed by coating the substrate 11 and the silicon substrate 11 with at least one of silicon carbide and silicon nitride by chemical vapor deposition!
(referred to as coating Ili 6) 12.

It is preferable that the silicon substrate 11 has a thickness of 100 to 1000 μm. Here, regarding the thickness of the silicon substrate 11 being 100 to 11000 LL, (i)
If it is less than 1100 u, the ceramic film 12 will be curved due to the difference between the t9 coefficient of expansion of the silicon substrate 11 and the coefficient of thermal expansion of the ceramic film 12 during cooling after the formation of the ceramic film 12 by chemical vapor deposition. Also (ii) 100
If the thickness exceeds 0 .mu.m, the time required for the etching process will be prolonged and the manufacturing cost will increase.

The reason why the central portion of the silicon substrate is removed in a circular shape is that if it is rectangular or the like, cracks are likely to occur from the corners due to thermal shock. Therefore, silicon substrate 11
The shape of the removed portion may be an ellipse or the like.

The ceramic film 12 is a ceramic I+! formed on the surface 11A of the silicon substrate 11. 12A and silicon substrate 11
, and a ceramic film 12c formed on the peripheral surface (also referred to as side surface) 11C of the silicon substrate 11. It is preferable that the ceramic films 12A-12c have the same composition so that the coefficients of thermal expansion can be easily approached.

The thickness of the ceramic l1i12A is preferably 0.1 to 20 um. The basis for this is (il 0.1 u
If it is less than m, the strength cannot be maintained and fii120
If it exceeds um, the ceramic film 12A is
A is easier to peel off.

The thickness of the ceramic film 12B is 0.85 of the thickness of the ceramic film 12A in order to keep the difference in thermal expansion coefficient within a suitable range.
It is preferable that it is 1.15 times. Here, the thickness of the ceramic film 12B is 0 of the thickness of the ceramic film 12A.
The reasons why the ratio is 85 to 1.15 times are as follows: (i) If it is less than 0.85 times, the thermal stress of the ceramic film 12B becomes too small compared to the thermal stress of the ceramic film 12A during cooling; and (ii) 1. If it exceeds 15 times, the thermal stress of the ceramic film 12B becomes too large compared to the thermal stress of the ceramic film 12A.

FIRST EXAMPLE Furthermore, with reference to FIGS. 1 and 2, the function of the first example of the ceramic thin film according to the present invention will be described in detail.

In the ceramic thin film IO according to the present invention, a ring-shaped silicon substrate 1i has a wall thickness of 100 to 1000+ um, and both its front surface 11A and back surface JIB are coated with at least one of silicon carbide and silicon nitride by chemical vapor deposition. homogeneous coating llMo12A,
12B is formed, the thickness of coating 12A is 0.1 to 20 μm, and coating 12A is
The film thickness of 2B is 0.8 of the film thickness of coating 12A.
5 to 1.15 times, it is possible to avoid bending of the silicon substrate 11 in the cooling process after chemical vapor deposition, and also to reduce the thermal expansion coefficient (and thus Thermal stress) can be brought closer to each other, and the region of the coating film 12A corresponding to the removed portion of the silicon substrate 11 can be prevented from being curved, and as a result, it can be used as a photomask in the drawing process on the semiconductor wafer. It is possible to suppress the shift in focus when

Construction and Use of the Second Embodiment Also, with reference to FIGS. 3 and 4, the structure and operation of the second embodiment of the ceramic thin film according to the present invention will be described in detail.

In the second embodiment, the edge portion of the silicon substrate 11 is
It has the same configuration as the first embodiment except that it is removed within the range of 73 or less.

As a result, the second embodiment not only has the effects of the first embodiment, but also can be made lighter in weight than the first embodiment.

Therefore, here, the same reference numerals are given to the members corresponding to those included in the first embodiment, and a detailed explanation of the structure and operation thereof will be omitted.

In addition, the manufacturing method of the first and second embodiments of the ceramic thin film according to the present invention will be explained in detail with reference to FIGS.

First, a disk-shaped silicon base 12iill having an appropriate thickness within the range of 100 to 1000 μm is prepared, and its front surface 11A and back surface 11B are mirror-finished (see FIG. 5(a)).

Next, the silicon substrate 11 is housed in a heat treatment furnace, and the surface 11A and side surface 11C of the silicon substrate 11 are coated with at least one of silicon carbide and silicon nitride by chemical vapor deposition to form a ceramic Uzp, 12c of 0.1 to 12c. 2
It is formed to have a film thickness of OL1m (see FIG. 5 (bl)).

Furthermore, the silicon substrate 11 is taken out from the heat treatment furnace, turned over, and a quartz glass 13 of an appropriate shape is placed thereon, and the silicon substrate 11 is placed in the heat treatment furnace again, and the back side of the silicon substrate 11]]B
At least one of silicon carbide and silicon nitride is coated on the surface by chemical vapor deposition to form a ceramic film 12B having the same quality as the surface 11A and having a thickness of 0.85 to 1.15 times (FIG. 5(c)). fdl). The quartz glass 13 has a disk-like shape when forming the ceramic thin film plate of the embodiment shown in FIG. This is a shape with added parts.

Finally, after taking out the silicon substrate 11 from the heat treatment furnace and removing the quartz glass 13, while placing the silicon substrate 11 in the heat treatment furnace again, a part of the silicon substrate 11 is exposed to MCI gas from the back surface 118 side. It is removed by a vapor phase etching process.

As a result, the front surface 11A and the back surface 11 of the silicon substrate 11
Ceramic films 12A to 1 are applied to B and side surface 11G.
2C is formed and ceramic I is formed on the removed part.
I! A ceramic thin film IO according to the present invention in which 12A is stretched can be produced.

In addition, the ceramic thin film according to the present invention will be described in detail by citing specific numerical values.

Jitsuwari 111 - A silicon substrate with a double wall thickness of 400 um and a diameter of 100 mm was mirror-finished on the front and back sides, and then placed in a heat treatment furnace.
Its surface temperature was maintained at 1300°C.

In this state, H as a carrier gas is applied to the heat treatment furnace.
2 gas, 5IC14 gas as a silicon source gas, and C, H, gas as a carbon source gas are heated at 15°C/
By supplying the solution at a rate of 1 minute, the surface and side surfaces of the silicon substrate were coated with a silicon carbide film having a thickness of 1 um.

After the silicon substrate has been cooled, it is taken out from the heat treatment furnace, and a quartz glass of an appropriate thickness is placed on the back surface in state b.
It was placed again in the heat treatment furnace, and its surface temperature was maintained at 1300°C. The shape of the quartz glass was circular.

In this state, H2 gas as a carrier gas, 5IC14 gas as a silicon source gas, and C3H gas as a carbon source gas are supplied to the heat treatment furnace for 50 seconds each at a total rate of 15 ff/min. Minute and 1 minute IO
By supplying for a period of seconds, film thicknesses of 0.85 μm, 1 μm and 1.1 μm were applied to the back side of the silicon substrate, respectively.
A 5 μm silicon carbide film was coated.

After cooling, the silicon substrate was taken out of the heat treatment furnace, the quartz glass was removed, and then placed in the heat treatment furnace again, and the back side was subjected to HC while maintaining the back side temperature at 1100°C.
Gas phase etching treatment was performed using I gas. As a result, the central portion of the silicon substrate was removed in a circular shape.

Through the above steps, a ceramic thin film according to the present invention was formed. In the ceramic thin film according to the present invention, as shown in Table 1, no variation in film thickness was observed in the coating film formed on the front and back surfaces of the silicon substrate. No internal cracks were observed, and no curvature of the silicon substrate was observed.
At the same time, the etching time was also significantly shortened! The thickness of the coating film formed on the surface of the five-glazed double silicon substrate is 1
0 μm, and the thickness of the coating IIN formed on the back surface of the silicon substrate is 8.5 μm and 1OLL, respectively.
Examples 1 to 1, except that m and 11.5 gm
3 was repeated.

As shown in Table 1, in the ceramic thin film according to the present invention, as in Examples 1 to 3, no variation in film thickness was observed in the coating film formed on the front and back surfaces of the silicon substrate. No internal cracks were observed in the coating film formed on the surface of the silicon substrate, and no curvature of the silicon substrate was observed, and the etching time was also sufficiently shortened.

The thickness of the coating film formed on the surface of the silicon substrate is 2.
0um, and the thickness of the coating film formed on the back surface of the silicon substrate is 17LLm20um and 20um, respectively.
Examples 1-3 were repeated, except that the thickness was 3 μm.

As shown in Table 1, in the ceramic thin film according to the present invention, as in Examples 1 to 3, no variation in film thickness was observed in the coating film formed on the front and back surfaces of the silicon substrate. No internal cracks were observed in the coating film formed on the surface of the silicon substrate, and no curvature of the silicon substrate was observed, and the etching time was also sufficiently shortened.

Comparative Example 12 The thickness of the coating film formed on the surface of the silicon substrate was 0.
．． 05LLm and 30μm, and the thickness of the coating film formed on the back surface of the silicon substrate is 0.05+um.
Examples 1-3 were repeated, except that the thickness was 30 μm.

In Comparative Example 1, there were large variations in the thickness of the coating film formed on the surface of the silicon substrate, and in Comparative Example 2, internal cracks were observed in the coating film formed on the surface of the silicon substrate.

Comparative Examples 3 and 4 The thickness of the silicon substrate was 1000 μm, and the thickness of the coating film formed on the surface of the silicon substrate was 10 μm, and the thickness of the coating film was 10 μm on the back surface of the silicon substrate. Examples 1-3 were repeated except that the film thicknesses were 5 μm and 10 μm.

In Comparative Example 3, the thickness of the silicon substrate was small, so the silicon substrate had a large curvature, and in Comparative Example 4, the etching time was prolonged.

The thickness of the coating film formed on the surface of the silicon substrate is 1
Examples 1 to 3 were repeated except that the thickness of the coating film formed on the back surface of the silicon substrate was 101 m, and the shape of the quartz glass was rectangular.

In this case, internal cracks were observed in the coating film formed on the surface of the silicon substrate.

Comparative Example 6 Comparative Example 5 was repeated except that the silicon substrate was rectangular and the quartz glass was circular in shape.

In this case as well, internal cracks were observed in the coating film formed on the surface of the silicon substrate.

Comparative Example 78 The thickness of the coating film formed on the surface of the silicon substrate was 1
0um, and the thickness of the coating film formed on the back surface of the silicon substrate is 8.0μm and 12μm, respectively.
Examples 1-3 were repeated, except that:

In this case, the curvature of the silicon substrate was 100 μm, which was large.

Comparative Example 9 10 The thickness of the coating film formed on the surface of the silicon substrate was 2
Examples 1 to 3 were repeated except that the thickness of the coating film formed on the back surface of the silicon substrate was 5 μm and 40 μm, respectively.

In this case, internal cracks were observed in the coating film formed on the surface of the silicon substrate. In addition, the curvature of the silicon substrate is
They were 450 um and 550 um, which were extremely large.

(3) Effects of the Invention As is clear from the above, the ceramic thin film according to the present invention, as specified in [Means for solving the problem], chemically coats at least one of silicon carbide and silicon nitride on one surface of a silicon substrate. A ceramic thin film created by coating by vapor deposition and then removing a part of a silicon substrate by etching from the other side, especially when the thickness of the silicon substrate is 100 to 11,000 u, and one side of the silicon substrate is coated by vapor deposition. On the other hand, the thickness of the ceramic film formed by coating is 0.1 to 20 μm, and on the other side of the silicon substrate, a ceramic film of the same quality as that on one side is applied by chemical vapor deposition, and the thickness is 0.85 to 1.15 times. (1) It has the effect of suppressing the bending of the silicon substrate due to the difference between the coefficient of thermal expansion of the silicon substrate and the coefficient of thermal expansion of the ceramic film. ) It has the effect of ensuring flatness, and as a result (iii) it has the effect of suppressing the occurrence of focal shift when used as a photomask when drawing electronic circuits on a semiconductor wafer.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a first embodiment of the ceramic thin film according to the present invention, FIG. 2 is a sectional view taken along the line ■-■ of the embodiment in FIG. FIG. 4 is a plan view showing a second embodiment of such a ceramic thin film; FIG. 4 is a cross-sectional view taken along line IV-IV of the embodiment in FIG. 3; FIG. 5(a)
-(f) are sectional views for explaining the manufacturing method of the embodiment in FIG. 1 and the embodiment in FIG. 3. IO・・・・・・・・・・・・ Ceramic thin film 11・・・・・・・・・・・・・Silicon substrate llA
.........Front surface 11B...Back surface 11C...Side surface 12...・・・・・・ Ceramic membrane 1
2A~12C・・・Ceramic pus 13 ・Quartz glass

Claims (1)

[Claims] A ceramic thin film created by coating one side of a silicon substrate with at least one of silicon carbide and silicon nitride by chemical vapor deposition, and then removing part of the silicon substrate by etching from the other side. The thickness of the silicon substrate is 100 to 1000 μm, the thickness of the ceramic film formed by coating on one side of the silicon substrate is 0.1 to 20 μm, and the other side of the silicon substrate is also coated with a chemical coating. A ceramic thin film characterized in that it is formed by vapor deposition to form a ceramic film of the same quality as one surface to a thickness of 0.85 to 1.15 times.