JPH0414467A - Ceramic substrate for thin film semiconductor devices - 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 [Technical Field] The present invention relates to a ceramic substrate for a thin film semiconductor device such as a semiconductor device, a thin film transistor, and a recording head incorporating a thin film transistor circuit.

[Prior art]

Currently, with the spread of portable word processors, laptop computers, etc., there is an increasing need for compact, lightweight, high-resolution printers.

Thermal printers are said to be more suitable for meeting these demands than regular dot matrix printers in terms of their size and printing sound. Furthermore, thermal printers are said to be more advantageous than dot matrix printers in terms of gradation display.

Typically, a thermal head consists of a heat generating section that performs printing and a driver IC that drives the heat generating section. The heating part is Ta:5i02
It is composed of resistors such as, and prints by generating heat when current is passed through it. Also, the driver IC is 32 dots or 64 dots.
It is a CMO8 or Bi-CMO8 chip consisting of a dot shift register and a power transistor. And they are connected by wire bonding.

In such a hybrid configuration, mounting restrictions such as wire bonding are imposed on higher resolution and an increase in the number of dots, making it difficult to downsize and lower the price of the thermal head.

Therefore, it is possible to form a thin film transistor circuit on the same substrate as the recording element (thermal head) instead of the integrated circuit chip such as CMO5 or B i -CMO8, and to make the heat generating part of the same material as the gate electrode of the thin film transistor. Therefore, the bonding process is omitted and T
a: The step of depositing a heating element such as SiO2 can be omitted, and it is possible to integrate the thin film transistor without changing the process steps. This makes it easy to make the thermal head /I\ type and increase the resolution, and it can be manufactured at low cost.

By the way, thin film transistor circuits are effective for large area devices and are generally fabricated on insulating substrates such as quartz. The advantages of quartz include flatness, large area, and high-temperature processability, but disadvantages include high cost and heat storage effect. In particular, the heat storage effect is a fatal drawback in thermal head type devices.

Tatoeha, JP-A No. 62-204964 is #4! A
The heating resistor and drive circuit are formed on the same substrate using a polycrystalline silicon thin film on a 9-substrate, and the drive circuit is made of TPT with a thin active layer, thereby reducing the size of the thermal head. However, when the insulating substrate is moved quickly at high speed due to the heat storage effect, the printing becomes black. In JP-A No. 62-242552, a thin film layer made of polycrystalline silicon is formed on a quartz substrate with a thickness of 10 to 800 μI, and a heating resistor and a driving circuit are formed on the same substrate. In this case, it is difficult to handle a quartz substrate with a thickness of 10 to 800 μm, and a thin film transistor process is not possible. In Japanese Patent Application Laid-open No. 62-248663, at least one thermal resistance layer is provided on at least a portion of a silicon substrate, and a thin film layer made of polycrystalline silicon is provided thereon, and this thin film layer is used to form a heating resistor and a parking circuit. However, because the silicon substrate has too good thermal conductivity, it cannot store enough heat for printing.

Therefore, a ceramic substrate with less heat storage may be considered.
Existing wrapping techniques do not provide as flat a surface as quartz (
For example, the surface unevenness of 1-quartz is ±30 mm, while that of α-AQ, O, which is a typical ceramic, is ±900 mm. ), stable thin film transistor circuits cannot be formed.

In other words, the flatness of the ceramic substrate is 1- at 300 m.
100ttvn, surface property is ±0.5 to ±10. um, and a glazed ceramic substrate with a wrapping finish and α-AQ20. Flatness of recrystallized substrate etc. is 300 fields 0
It is about 10μ■1, and the superficiality is about ±1000 people, and it is 9.
It is not suitable for manufacturing thin film transistors.

〔the purpose〕

The object of the present invention is to solve the above problem, namely to provide a ceramic substrate, in particular α-AQ20. To provide a ceramic substrate for a thin film semiconductor device, in which the flatness of a recrystallized substrate, a glazed ceramic substrate, etc. is improved to the extent that a stable thin film transistor circuit can be formed, and, for example, a good thin film transistor circuit integrated recording head can be formed. be.

〔composition〕

The flatness of the present invention is 3001 m10 and 100 pm or less.

Preferably 5 μm or less, particularly preferably 3 μm or less,
Surface properties are ±10μm or less, preferably 50r+m or less,
In particular, the present invention relates to a ceramic substrate for a thin film semiconductor device, which preferably has a thickness of 10 nm or less.

The flatness mentioned above means that the flat surface of 300 fields 1w110 is 100μm.
It means that it is within the range. If this exceeds the specified value, uneven resist coating may occur during semiconductor device manufacturing.
Problems occur when the pattern accuracy during exposure and the specifications required by the manufacturing equipment are exceeded. Generally 10μm
If it is below, no problem will occur at all.

In addition, the surface quality is the depth of peaks and valleys when scanning a part of a plane, and in thin film devices, problems will occur if the thickness is not within the minimum thickness of about 1710 mm (therefore, the surface quality is (This is in accordance with JIS It 0601-1982.)

Ceramic substrates used in the present invention include sol-coated ceramic substrates, which will be described later, as well as glazed ceramic substrates that have been surface-treated using a lapping technique, and α-A
β20. Examples include recrystallized substrates.

FIG. 1 is a sectional view of a specific example of a ceramic substrate for a thin film semiconductor device according to the present invention, in which a flattened layer N2 is formed on the entire surface of an α-AQ203 recrystallized substrate 1. FIG. 2 is an enlarged view of portion A in FIG. 1.

The formation of the planarization layer 2 will be explained.

When using quartz as the base material of the flattening layer 2, for example, ethyl silicate is used, and purified water is added to and hydrolyzed while adjusting the pH. As a result, a high-purity silica-containing sol with a particle size of 3000 Å or less is obtained. The purity of this sol depends on the purity of the raw materials used, such as the purity of the silicic acid ethyl ester. The pH adjustment controls the reaction rate and the particle size of the fine silica particles. This high-purity sol is used to coat a ceramic substrate, such as an α-AQ, O, recrystallized substrate, by a dip method. The coating may be applied to one side, both sides, or the entire surface of the substrate including the sides.

After the coating, it is dried in air at 60° C. for 200 hours, and then subjected to high temperature treatment. Silica fine particles do not require high temperatures of 2200°C, but 750°C to 120°C.
0℃ is fine.

The flatness of the surface of the flat layer 2 is 6 at 300 cm.
.mu.m, the surface roughness is ±30 μm, and the ceramic substrate with the layer can form a stable thin film transistor circuit.

In addition to the above-mentioned 5in2, TiO is used as the base material of the flattening layer.
2 can also be used, in which case TiD-OC3H7
) 4 is hydrolyzed. Other metal alkoxides or semiconductor alkoxides such as Si alkoxides [e.g.
5i(OR) where R is methyl, ethyl, propyl, etc.) can also be used. Alkoxide can be hydrolyzed,
It becomes glassy after the firing process.

Hereinafter, a case in which a thin film transistor is formed on a ceramic substrate provided with this flat layer will be explained with reference to FIG.

After depositing a polycrystalline silicon film on the planarization layer 2 of the ceramic substrate 1 by the LPCVD method, only the active layer region 3 is left,
The rest will be removed by etching.

A gate electrode 5 and a thermal head (hereinafter abbreviated as TPH) heating element 6 are provided via a gate insulating film 4 such as 5in2. The source region is self-aligned with respect to the gate electrode 5.
A drain region 7 is formed. An electrode 9 made of aluminum-based metal is formed via an interlayer insulating film 8 such as SiO□.

In addition, if the maximum temperature in the TPT process is 900°C or higher, α-AQ20. It is preferable to use a recrystallized substrate provided with a flattening layer.

As a specific means for improving flatness, the above-mentioned sol coating method is the most preferred, but other methods are also available.

(i) Glazed glass bonding method (however, no heat process above 350°C is applied) (ii) Method of depositing several micrometers by CVD method and then flattening by etching back etc. (iii) Using SiCQ4 gas 5 by calcining spray
There are methods of forming an in2 preform.

〔effect〕

The ceramic substrate having a planarization layer of the present invention allows a thin film transistor circuit and a recording element (TPH) to be formed on the substrate, and can also prevent printing from turning black due to heat accumulation.

Furthermore, due to the improvement of surface properties by the planarization layer, in the case of high-speed instantaneous operation of part of the shift register of 1728 bits, the clock frequency operates at IMHz, and a stable TPT circuit can be fabricated.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a specific example of a ceramic substrate for a thin film semiconductor device of the present invention, FIG. 2 is an enlarged sectional view of part A in FIG. 1, and FIG. 3 is a ceramic substrate for a thin film semiconductor device of the present invention. FIG. 3 is a cross-sectional view of a case where a thin film transistor is formed thereon. 1... Ceramic substrate 2... Flat layer 3... Active layer region 4... Gate insulating film 5... Gate electrode 6... TPH heating element 7... Source/drain region 8...・Interlayer insulating film 9... AQ system electrode Diagram Δ Diagram 2 Imaichi - Funeral diagram

Claims (1)

[Claims] 1. A ceramic substrate for a thin film semiconductor device, characterized in that the flatness is 100 μm or less at 300 mm^□, and the surface roughness is ±10 μm or less.