JPH0473162A - Silicon substrate having porous silicon oxide layer and manufacture thereof - Google Patents

Abstract

PURPOSE:To make a warp of a silicon substrate small by studding layers consisting of porous silicon oxide on the surface of the silicon substrate. CONSTITUTION:On the surface of a silicon substrate 20, POS layers 26 consisting of porous silicon oxide are studded. A plane figure of the POS layer 26 is a square made by rounding corners 20a. A radius of the rounded corner 20a is set to 30mum or more. The magnitude of the POS layer 26 is to be width Xlength = about 1mm X 50mm. The interval between those POS layers 26 is set to be 2mm or more. In this silicon substrate 20, since the POS layers 26 are studded, residual internal stress generated in the POS layers 26 is dispersed. Accordingly, a warp of the whole substrate 20 becomes small in this silicon substrate 20.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention is applicable to substrates such as thermal heads, optical IC single switches, etc. that constitute thermal transfer printers and thermal printers;
In other words, it relates to a silicon substrate that can be suitably used as a substrate that requires both heat insulation and heat dissipation properties, and a manufacturing method thereof.In particular, it relates to a silicon substrate that can be suitably used as a substrate that requires both heat insulation and heat dissipation properties. The present invention relates to a formed Noricon substrate and a manufacturing method thereof.

"Conventional technology" FIG. 18 shows a conventional thermal head.

This thermal head has a heat storage layer 2 made of glass glaze partially formed on an alumina substrate l. A heating resistor layer 3 is formed on the heat storage layer 2 and the substrate l. A conductor layer 4 for supplying current to this layer 3 is formed on this heating resistor layer 3 . On the substrate 1, a heating section 6 is formed in a dot shape by the conductor layer 4 and the resistor layer 3. A protective layer 5 is laminated on these to protect them from oxidation and wear.

This thermal head is used while being pressed against a recording medium (not shown) such as an ink ribbon or thermal paper. When a current is applied to the heat generating section 6 of the thermal head to generate heat, it is possible to thermally transfer the ink of the ink printer or to color the recording medium.

As a means of improving the thermal efficiency of such a thermal head, there is a means of increasing the heat storage amount by increasing the heat capacity by increasing the thickness of the heat storage layer 2 made of glass glaze.

However, when the heat storage layer 2 made of glass glaze is made thicker in this manner, the time required for the temperature to drop after heat generation becomes longer, resulting in a problem that the thermal responsiveness of the thermal head is impaired.

In order to avoid such problems and improve the thermal efficiency of the thermal head, it is recommended to provide a heat storage layer with low thermal conductivity and low heat capacity.Porous materials are suitable for forming such a heat storage layer. Porous Oxidized 5il
icon (hereinafter abbreviated as POS) is known. P.O.
S has high heat resistance and sufficient mechanical strength.

As a thermal head in which a heat storage layer is formed using POS, there is one proposed in JP-A-63-257652. This thermal head, as shown in Fig. 19,
The heat storage layer 12 formed by POS is attached to the silicon substrate 1.
It is formed over the entire surface of 1. And this P.O.
On the heat storage layer 12 made of S, a non-porous silicon oxide layer I3 is provided.
, a heating resistor layer 3, a conductor layer 4, and a protective layer 5 are sequentially laminated.

As a method for manufacturing the silicon substrate 11 that forms this thermal head, an electrolytic solution consisting of hydrofluoric acid, alcohol, and water (
The silicon substrate 11 is anodized in a hydrofluoric acid aqueous solution to form porous silicon.
A method is known in which a layer made of PS (hereinafter abbreviated as PS) is formed and then this layer made of PS is thermally oxidized.

"Problem to be solved by the invention" By the way, the silicon substrate mentioned above! In 1, the volume increases approximately 22 times when PS is thermally oxidized to become POS, and internal stress (compressive stress) remains in the formed heat storage layer I2, causing the Noricon substrate 11 to warp greatly. There's a problem.

When the substrate II is actually manufactured, a layer consisting of POS (
When the heat storage layer +2) is formed to have a thickness of 25 μm, the substrate 11
warps 1 mm per inch. This warpage is about 10 times that of a commercially available alumina ceramic substrate. Because such large warpage occurs, the above-mentioned Noricon substrate II lacks practicality.

An object of the present invention is to provide a silicon substrate having a layer made of porous silicon oxide (POS) with less warpage, and to provide a manufacturing method thereof.

"Means for Solving the Problems" A silicon substrate having a porous silicon oxide layer according to the present invention has a layer made of porous silicon oxide interspersed on the surface portion of the silicon substrate.

The method for manufacturing this Noricon board is to cover the surface of the Noricon board with a mask, except for the scattered parts to be processed.
A suitable method is to anodize the silicone substrate in an aqueous hydrofluoric acid solution to form porous silicone in the portion to be treated that is not covered with a mask, and then oxidize the formed porous silicone.

As the mask, photorenost or an oxide film is suitably used.

As the photoresist, a photoresist is used because it has excellent acid resistance. Photorenosts with excellent acid resistance include cyclized butadiene rubber-based polymers (eg, cyclized polybutanoene) and cyclized isoprene rubber-based polymers.

A negative resist for mesa etch, etc. whose main component is a cyclized hydrocarbon polymer such as remer (for example, cyclized polyisoprene) is preferably used.

Further, as the oxide film, tantalum oxide (Ta20s)
or a film made of chromium oxide (CRTO 3).

The method of oxidizing porous silicon to make porous silicon oxide involves heating the substrate to 850~
A thermal oxidation method in which the substrate is heated to ~1000° C., a method in which the substrate is exposed to plasma, etc. can be suitably used.

In the method for manufacturing a silicon substrate of the present invention, materials that can be used as a mask are not limited to the tantalum oxide, chromium oxide, and photoresist, but also various passive films and materials that are not attacked by hydrofluoric acid. Insulators such as silicon nitride and sialon can also be used.

When a silicon nitride film or a sialon film is used as a mask, pattern formation and removal of the silicon nitride can be performed by dry etching. Furthermore, molybdenum (Mo), tungsten (W), and the like can be used as mask materials that are not attacked by hydrofluoric acid. When using MO or W as a mask material, it is desirable to form the mask thick.

"Function" In the silicon substrate of the present invention, since layers made of PO8 are scattered, residual internal stress (compressive stress) occurring in the POS layer is dispersed.

``Example'' (Example I) FIG. 1 shows an example of a silicone substrate having a porous oxidized silicone layer according to the present invention.

A layer 26 made of porous oxidized silicone (hereinafter referred to as PO9 layer) 26 is scattered on the surface portion of the noricon substrate 20. The planar shape of each PO5 layer 26 is a rectangular shape with rounded corners 20a, as shown in FIG. The radius of the rounded corner 20a is set to 30 μm or more. Further, the size of each POS layer 26 is approximately 1 mm in width x 1 mm in length x 50 mm. Also these 20
The interval between the eight layers 26 is set to 2 mm or more.

In this silicon substrate 20, since the PO5 layers 26 are scattered, the residual internal stress (compressive stress) generated in the POS layer 26 is dispersed. Therefore, in this silicon substrate 20, the warpage of the entire substrate 20 is reduced.

Further, in this silicon substrate 20, the corner 2 of the POS layer 26
Since 0a is rounded, there is a corner 20a on the PO5 layer 26.
This will prevent cracks from forming.

(Example 2) Next, a method for manufacturing the silicon substrate 20 of Example I using a tantalum oxide mask and a thermal head using this silicon substrate 20 will be explained with reference to FIGS. 3 to 9. do.

This manufacturing method ■ First, a Noricon board 20 shown in FIG. 3 was prepared.

This silicon substrate 20 has a resistivity of 0. O19・cm
A P-type substrate was used.

(2) Next, as shown in FIG. 4, tantalum [21] was sputtered onto this silicon substrate 20.

The thickness of this tantalum film 21 was preferably about 0.1 to 0.5 μm. The tantalum film 21 in the region 22 where the heat storage layer is to be formed was etched by photolithography to expose the surface of the silicon substrate 20.

(2) Next, thermal oxidation was performed in the atmosphere at a temperature of 500 to 1000 DEG C. to form a tantalum oxide film 23 on the surface of the tantalum film 21, as shown in FIG.

The thickness of this tantalum oxide film 23 depends on the temperature during the oxidation treatment. Further, at this time, the surface of the silicone in the heat storage layer forming region 22 was also oxidized, and a 5iOz film 24 was formed.

■ Next, a concentration of 2 (lvt%) is placed in an electrolytic tank with a platinum plate as the cathode.
A hydrofluoric acid aqueous solution was added thereto, and the above-mentioned Norikono substrate 20 was used as an anode to face the platinum plate, and anodization treatment was performed using direct current. The treatment conditions were a current density of 50 mA/''cm' and a treatment time of 20 minutes.

Since tantalum oxide is passive and is not corroded by hydrofluoric acid, the tantalum oxide film 23 formed on the Noricon substrate 20 reliably serves as a mask. Then, a porous Noricon layer with a thickness of 40 μm and a porosity of 80% (
Hereinafter, 25 layers (hereinafter referred to as 28 layers) were formed. This PS layer 2
The thickness of No. 5 could be freely controlled by changing the anodization treatment time.

When anodizing as described above, the oxide tank film 23
However, since the area 22 where the heat storage layer is to be formed is small, applying a small voltage of approximately 0.4 V will be sufficient to anodize the surface of the Noricon substrate in this area 22. Required current density, approximately 50 mA
/cm". Therefore, dielectric breakdown does not occur during anodization.

■ Next, after thorough cleaning, as shown in Figure 7,
The tantalum film 21 and tantalum oxide film 23 on the silicon substrate 20 were removed by dry etching.

■ Next, after thorough cleaning, place in humidified oxygen at 85%
Thermal oxidation was performed at 0°C to 1000°C to oxidize the 28 layers 25.

When this PS layer 25 is oxidized, porous silicon (
As PS) changed to porous silicon oxide (POS), the volume increased, and as shown in FIG. 8, a protruding POS layer 26 was formed. The protruding height of the convex portion of this 208 layer 26 is 3 to 5 μm.

During this oxidation treatment, the surface of the Noricon substrate 20 is also oxidized, and an 8-layer film with a thickness of 0.2 to 05 μm is formed around the POS layer 26.
10. A film 24 was formed.

The silicon substrate 20 formed in this manner may be coated with a nonporous insulating film such as nonporous silicon oxide or sialon by sputtering, if necessary.

FIG. 9 shows the silicon substrate 2 manufactured as described above.
This figure shows a thermal head using 208 layers 26 of 0 as the heat storage layer. This thermal head is Ta2N
, Ta Cr N, Ta 5ift, etc. to a thickness of 0.05 to 0 on the silicon substrate 20.
A heating resistor layer 3 having a thickness of 3 μm is formed. On this heating resistor layer 3, a conductor layer 4 having a thickness of 1 to 2 μm is provided by vapor-depositing AQNi-Cr/Au. At the protruding portion of the POS layer 26, the conductor layer 4 is etched and removed by photolithography to form the heat generating portion 6. The heating resistor layer 3 and the conductor layer 4 are connected to each other on both sides of the POS layer 26. By the outermost part of this thermal head, S +O
t/T a205. A protective layer 5 having a thickness of 5 to 7 μm formed by sputtering SiAlON or the like is provided.

According to the manufacturing method of this example, the tantalum oxide film serving as a mask is resistant to the hydrofluoric acid aqueous solution used during anodizing treatment, so the Noricon substrate of Example 1 can be reliably manufactured. .

(Example 3) Next, a second example of the method for manufacturing a silicon substrate will be described.

The first half of this manufacturing method is the same as steps (1) to (4) of Example 2 above.

The manufacturing method of this example differs from the method of Example 2 as follows:
After the silicon substrate 20 is anodized to form the PSFi 25 as shown in FIG. 6, the PS layer is immediately formed without removing the tantalum film 21 and tantalum oxide film 23 (without performing the step 25 was thermally oxidized at 850° C. to 10.00° C. to form the PO5 layer 26.

The silicon substrate 20 manufactured in this way is
As shown in the figure, the outer periphery of the 208 layer 26 and the portion where the 208 layer 26 is not formed are covered with the tantalum film 21 and the tantalum oxide film 23.

When a heating resistor layer 3, a conductor layer 4, and a protective layer 5 are formed on this silicon substrate 20 in the same manner as in Example 2, a thermal head shown in FIG. 11 is obtained.

According to this manufacturing method, the silicon substrate 20 on which the POS layers 26 are scattered can be efficiently manufactured.

(Example 4) A silicon substrate was manufactured using a method different from that of Example 3 except that chromium was sputtered instead of tantalum.

According to this manufacturing method, the chromium oxide film obtained by oxidizing the chromium film formed on the silicon substrate 20 is resistant to the hydrofluoric acid aqueous solution used in the anodization treatment, so the 208 layer 26 It is possible to efficiently manufacture a silicon substrate 20 dotted with .

(Example 5) FIGS. 12 to 17 show each step of a fourth method for manufacturing a silicon substrate.

(2) In this example, first, a silicon substrate 20 shown in FIG. 12 was prepared. This substrate 20 has a resistivity of 0.
A P-type substrate with a diameter of 0.010 cm was used.

■ Next, as shown in FIG. 13, a photoresist 32, for example a negative resist (CBR-M90
1: manufactured by Nippon Synthetic Rubber Co., Ltd.) was applied and patterned by photolithography.

■ Next, a 20 wt % aqueous solution of hydrofluoric acid was placed in an electrolytic cell with a platinum plate as a cathode, and anodization was performed for 16 minutes at a current density of 50 mA/cm' direct current with the silicon substrate 20 as an anode. As shown in FIG. 14, 1) A PS layer 25 was formed with a depth of 32 μm at the opening of the resist 32 and a porosity of 80%.

The periphery of the formed PS layer 25 slightly extended into the area covered with the photoresist 32. The depth of this part is
The depth gradually became shallower as the distance from the opening of the photoresist 32 increased.

(2) Next, the photoresist 32 was removed to obtain the state shown in FIG. 15. The photoresist 32 could be easily removed using a commercially available stripping solution, hot sulfuric acid (sulfuric acid + hydrogen peroxide solution).

■ After this, thoroughly wash and store in humidified oxygen for 85 minutes.
Thermal oxidation was performed at 0°C to 1000°C to oxidize the PS layer 25. This oxidation increased the volume of the PS layer 25 and formed a POS layer 26 protruding from the surface of the substrate 20. The surrounding area of this PO5 layer 26 was gradually becoming thinner. P.O.
The height of the eight layers 26 was 3 to 5 μm. Also this POS
As shown in FIG. 16, a 0.2-0.5 μm thick Sin layer was formed on the surface of the silicon substrate 20 around the layer 26.

After that, a heating resistor layer 3, a conductor layer 4,
By sequentially laminating the protective layers 5, the thermal head shown in FIG. 17 is obtained.

According to this manufacturing method, since the adhesive force of the photoresist 32 to the silicon substrate 20 is moderately weak, the electrolyte slightly penetrates into the part covered by the photoresist 32 during anodization, and this part is also shallowly anodized. be done. As a result, the formed PS layer 25 and the PO8 layer 26 obtained by oxidizing it have a shape in which the peripheral portion gradually becomes thinner toward the outside, and the internal stress within the POS layer 2 layer 6 is reduced. Concentration on the outer periphery of the PO9 layer 26 can be avoided. Therefore, the silicon substrate 20 manufactured by this manufacturing method has little warpage even around the POS layer 26, making it practical.

"Effects of the Invention" As explained above, the silicon substrate having a porous silicon oxide layer of the present invention has a layer made of porous silicon oxide dotted on the surface portion of the silicon substrate. Residual internal stresses (compressive stresses) occurring in the layer are dispersed. Therefore, in the silicon substrate having the porous silicon oxide layer of the present invention, the warpage of the entire silicon substrate is extremely small.

In addition, as a method for manufacturing a silicon substrate of the present invention, the surface of the silicon substrate is covered with a mask except for the scattered portions to be treated, and the silicon substrate is anodized in a hydrofluoric acid aqueous solution so that the silicon substrate is not covered with the mask. If a manufacturing method is adopted in which porous glue is generated in the portion to be treated and then the formed porous glue is prevented from being oxidized, it is possible to reliably produce a glue board with porous oxidized glue layers interspersed thereon.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of a silicon substrate having a porous oxidized silicone layer according to the present invention. FIG. 2 is an enlarged view showing section A in FIG. 1. 3 to 8 are cross-sectional views for explaining each step of the manufacturing method of Example 2. FIG. FIG. 9 is a sectional view showing a thermal head manufactured in Example 2. FIG. 10 is a sectional view showing one step of the manufacturing method of Example 3. FIG. 11 is a sectional view showing the thermal head manufactured in Example 3. 12 to 16 are cross-sectional views showing each step of the manufacturing method of Example 5. FIG. FIG. 17 is a sectional view showing the thermal head manufactured in Example 5. FIG. 18 is a sectional view showing a conventional thermal head in which the heat storage layer is formed of glass glaze. FIG. 19 is a sectional view showing a conventional thermal head in which the heat storage layer is formed of porous silicon oxide. 20... Silicon substrate, 23... Tantalum oxide film, 25... Porous silicon layer (PS layer),
26...Porous silicon oxide layer (POS layer), 32
...Photoresist.

Claims (2)

[Claims] (1) A silicon substrate having a porous silicon oxide layer, characterized in that the surface portion of the silicon substrate is dotted with a layer made of porous silicon oxide. (2) Cover the surface of the silicon substrate with a mask, except for scattered areas to be treated, and anodize the silicon substrate in an aqueous solution of hydrofluoric acid to form porous silicon on the areas to be treated that are not covered with the mask. 1. A method for producing a silicon substrate having a porous silicon oxide layer, the method comprising: forming a porous silicon oxide layer, and then oxidizing the formed porous silicon.