JPH05296962A - Manufacture of heat conduction detector - Google Patents

Abstract

PURPOSE:To miniaturize a filament with a simple process easily by forming a buried layer on a substrate by the ion implantation method and then eliminating an unneeded part by etching. CONSTITUTION:The surface of a high-resistance Si substrate 1 is converted with a photo resist film 21 with a pattern where a part corresponding to a part where the filament is formed has a rectangular window and a dopant (B) is subjected to high-energy ion implantation, thus forming a buried layer 1a with a thickness of approximately 1mum at a depth of approximately 1mum from the surface within the substrate 1 and activating the implanted B electrically by heat treatment. Then, a resist film 22 is formed and an unneeded part between sides of the buried layer 1a is eliminated by etching. After that, the surface of the substrate 1 is covered with a resist film 23 with windows at corresponding positions of both edges of the buried layer 1a, high-concentration layers 3a and 3b are formed by performing ionimplantation of B, and then electrodes 4a and 4b are deposited on them. Further, an unneeded part of the substrate 1 is eliminated by etching from the rear-surface side, thus obtaining the filament 2 where the buried layer 1a is protected by the substrate material Si.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal conductivity detector (TCD) used in gas chromatography and the like.
tive Detector).

[0002]

2. Description of the Related Art As a heat conduction detector used in gas chromatography or the like, as shown in FIG. 7, a filament element 102 is made of a tungsten alloy or a tungsten-rhenium alloy.
There is a structure in which 02 is installed inside the cell 101 having a volume of about 0.05 to 2.0 ml. In addition, as shown in the vertical sectional view of FIG. 8A and the horizontal sectional view of FIG.
There is a cell (volume: about 5 × 10 ^-6 ml) 111 inside, etc. (“Measurement Technology” '89 special edition manuscript No. AZ10-14).

Of these, the structure shown in FIG.
If the filament is placed in a carrier gas with a large thermal conductivity such as helium in a state where a current is applied to the filament to heat it, and the sample component passes through it,
Since the thermal conductivity of the sample component is smaller than that of the carrier gas, the filament temperature rises. The detector is based on the principle that the thermal conductivity of the sample component is known by measuring the change in the resistance value of the filament due to this temperature rise.
In addition, in the structure of FIG.
Is protected by an insulating film 113 in order to prevent the chemical durability of the filament from lowering due to contact with gas.

[0004]

In the heat conduction detector, miniaturizing the sensor, that is, the filament, has a merit in that the response speed and the sensitivity are increased because the heat capacity is reduced. In the detector having the structure shown in FIG. 7, it is difficult to miniaturize the filament due to the limit of machining.

On the other hand, in the structure shown in FIG. 8, since the filament is manufactured by the micromachining technique, it is possible to miniaturize the filament, but there remains a problem that the manufacturing process is complicated. That is, in order to obtain a filament in a floating state from a Si wafer, first, a sacrificial layer to be removed in the future is laminated on the Si wafer, an insulating film is deposited on the sacrificial layer, and then a Ni thin film is formed. Is deposited and patterned, the Ni filament obtained by this patterning is covered with an insulating film, and then the insulating film is patterned by etching and the sacrificial layer is removed by etching. is necessary.

The present invention has been made in view of the above points, and an object thereof is to easily miniaturize a filament, which is a temperature-sensitive portion of a heat conduction detector, by a simple process. To provide a method.

[0007]

In order to achieve the above-mentioned object, in the first method of the present invention, FIG.
As shown in (a), a dopant (for example, B) is introduced into the semiconductor (Si) substrate 1 by an ion implantation method to form a buried dopant layer 1a having a shape corresponding to the filament to be manufactured (a), and thereafter, Mask 2 with a predetermined pattern
2, 23 is used to etch the semiconductor substrate 1,
By leaving the embedded dopant layer 1a covered with the substrate material, the filament 2 used as the temperature sensing portion of the heat conduction detector is obtained.

Further, in order to achieve the same object, in the second method of the present invention, as shown in FIG. 6 corresponding to the embodiment, by implanting ions into the insulating substrate 11,
A buried conductive layer 11a having a shape corresponding to the filament to be manufactured is formed, and thereafter, the insulating substrate 11 is etched using a mask having a predetermined pattern, and the buried conductive layer 11a is covered with the substrate material. If left, the filament 1 used as the temperature sensing part of the heat conduction detector
Get 2.

[0009]

In the ion implantation method, the implantation energy is set to a high energy (for example, about 200 keV or more) so that the concentration peak has a distribution deep in the target surface, for example, at a depth of about 2 μm. Ions can be implanted. Further, by the ion implantation, the thickness of the buried layer effective as the dopant layer can be set to, for example, about 1 μm (see FIGS. 4 and 5 described later).

Further, the buried dopant layer formed on the semiconductor substrate by the ion implantation method has an electric resistivity different from that of the non-implanted region, and it becomes possible to flow a current only to this portion.

From the above, after performing high-energy ion implantation to form a buried dopant layer in a semiconductor substrate, unnecessary portions of the substrate are removed by etching, so that the filament 2 protected by the substrate material is removed. Obtainable.

On the other hand, when ions are implanted with high energy using an insulating substrate as a target, the thickness is about 1 as in the previous case.
It is also possible to form a buried conductive layer having a thickness of about μm, and in this case also, the filament 12 protected by the insulator can be obtained.

[0013]

【Example】

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining the procedure of an embodiment of the first method of the present invention.

First, a high-resistance Si substrate is thermally oxidized, and then photolithography is performed, as shown in FIG.
The surface of the high resistance Si substrate 1 is patterned as shown in FIG.
That is, a portion corresponding to the filament forming portion is covered with a photoresist film 21 having a pattern in which a rectangular wave window is opened, and in this state, the high resistance Si substrate 1 has a dose amount of 4 × 1.
B of 0 ¹⁴ ions / cm ² is ion-implanted at 1 MeV. By this high-energy ion implantation, as shown in FIG. 4 to be described later, the Si substrate 1 has a dopant concentration of 1 × 10 3 from a position at a depth of about 1 μm to a thickness of about 1 μm.
The buried layer 1a of ¹⁷ ions / cm ³ or more is formed. After this, in order to electrically activate the ion-implanted B,
Suitable heat treatment (eg RTA (Rapid Thermal Anneal):
1000 ℃, 10sec).

Next, a photoresist film 22 having a pattern as shown in FIG. 2 (b) is formed on the surface of the Si substrate 1 by photolithography [FIG. 1 (b)], and then HF is used as an etchant for the Si substrate. 1 etching,
Unnecessary portions between the respective sides of the buried layer 1a are removed.

Then, Si is formed by photolithography.
The surface of the substrate 1 is covered with a photoresist film 23 having windows in the pattern shown in FIG. 2C, that is, at positions corresponding to both ends of the buried layer 1a (C), and B is ion-implanted. , The high concentration layer 3 at both ends of the buried layer 1a.
After forming a and 3b and then performing appropriate annealing, as shown in (d), electrodes 4a and 4b are vapor-deposited on the high-concentration layers 3a and 3b, respectively, to ensure ohmic contact. .. When the electrode is formed, the thermal oxide film (S
iO ₂ ) is removed.

Then, by etching from the back surface side to remove unnecessary portions of the Si substrate 1,
As shown in (e) of FIG. 1 and the plan view of FIG. 3, the filament 2 having a structure in which the embedded layer 1a is protected by the substrate material Si.
Can be obtained. After the production of such a filament 2 is completed, the anodic bonding method used in the micromachining technique or the like is adopted, and a glass plate having a predetermined shape is bonded to the Si substrate 1 to obtain the structure shown in FIG. A heat conduction detector having such a structure is obtained.

Next, a calculation example of the resistance value of the filament manufactured by the above process will be described below with reference to FIGS. 4 and 5. FIG. 4 shows that Si is the target and B is
FIG. 5 is a graph showing a simulation result of a dopant profile when ions are implanted at 1 MeV and 4 × 10 ¹⁴ ions / cm ² , and FIG. 5 shows the resistivity at 300 K with respect to the concentration of the dopant (B) introduced into Si (300 K). It is a graph which shows change.

Considering the effective thickness of the buried layer as a filament in the injected dopant distribution up to the region where the resistivity increases by one digit from the peak, the corresponding dopant concentration is shown in the graph of FIG.
The area is two digits lower than (10 ¹⁹ cm ^-3 ). The thickness of such region or dopant layer is about 1 μm from FIG.
It will be about m. Moreover, since the implantation is performed with a high energy of 1 MeV, the effective dopant layer is about 2 μm from the Si surface.
The depth of m is embedded as a concentration peak.

The resistance R at both ends of the filament can be expressed by R = ρ (L / w · t) ... (1). Where ρ is the resistivity of the buried layer, L is the filament length, w is the filament line width,
t: filament thickness. In this equation (1), t is the above-mentioned effective thickness of 1 μm: 1 × 10 ⁻⁴ (cm), and
L = 100 × 10 ⁻⁴ (cm) and w = 5 × 10 ⁻⁴ (cm). Furthermore, when the resistivity of the buried layer is represented by a dopant concentration of 1 × 10 ¹⁸ , ρ = 5 × 10 ^-2 (Ω / cm
), And from these values, R = 10 [kΩ]. As described above, a desired resistance value R can be obtained by appropriately selecting the filament length, the filament line width, the dopant implantation amount, and the like.

By the way, it is generally said that the sensitivity of the filament of the heat conduction detector is higher when a large amount of current is passed. Here, when ion implantation with high energy (for example, 1 MeV) is performed, the distribution of implanted ions in the depth direction tends to widen, as shown in FIG. Thus, it is effective to reduce the resistance value of the filament to be manufactured, that is, to facilitate the flow of current, and therefore the method of the present invention makes it possible to manufacture a heat conduction detector having good sensitivity.

Further, according to the above-mentioned embodiments, since Si is used as the substrate material, it is possible to easily form an oxide film (SiO ₂ ) on the surface of the substrate by thermal oxidation. It is possible to obtain a filament having excellent durability.

As the ions to be implanted, in addition to B,
Other dopant ions such as P or As may be used. Next, an embodiment of the second method of the present invention will be described below with reference to FIG.

First, as shown in (a), a photoresist film 31 having the same pattern as that used in the previous embodiment is formed on the insulating ceramic substrate 11, and metal ions such as Al are formed in this state. Are ion-implanted to form a buried conductive layer 11a. This ion implantation is high-energy ion implantation of 200 keV or more as in the previous embodiment.

Then, by the same process as in FIGS. 1B to 1D, substrate etching, formation of a conductive layer for contacting the buried layer, and formation of electrodes are sequentially carried out, as shown in FIG. 6B. After obtaining the structure and electrodes 14a, 14b, the substrate 11
By carrying out etching from the back side of the filament 12, it is possible to obtain the filament 12 having the structure shown in FIG.

The ions implanted to form the conductive layer may be Al or another metal such as Au. Alternatively, the conductive layer may be formed by implanting C ions with a C-rich substrate such as SiC as a target.

[0027]

As described above, according to the present invention,
An embedded layer is formed on a substrate by an ion implantation method applied to microfabrication such as a semiconductor device manufacturing process,
After that, the unnecessary part of the substrate is removed by etching to obtain the filament of the heat conduction detector. Therefore, the sacrifice layer formation and the metal thin film deposition before and after the deposition, which were required when the filament was formed by the micromachining technology, were obtained. No need for complicated processes such as deposition of insulating film in
This simplifies and facilitates the process of miniaturizing the filament as compared with the conventional process.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a procedure of an embodiment of a first method of the present invention.

FIG. 2 is a photoresist film 21 used in the embodiment,
The figure which shows the pattern shape of 22 and 23

FIG. 3 is a plan view showing the structure of a filament of a heat conduction detector obtained by the procedure of FIG.

FIG. 4 is a graph showing an example of a dopant profile when 1 MeV B is implanted into Si.

FIG. 5 is a graph showing the change in resistivity at 300 K with respect to the concentration of the dopant (B) introduced into Si.

FIG. 6 is a diagram illustrating a procedure of an embodiment of the second method of the present invention.

FIG. 7 is a diagram showing a conventional structure example of a heat conduction detector.

FIG. 8 is a view showing a conventional structure example of a heat conduction detector miniaturized by micromachining technology.

[Explanation of symbols]

 1 ... High resistance Si substrate 1a ... Embedding layers 21, 22, 23 ... Photoresist film 2 ... Filaments 3a, 3b ... High concentration layers 4a, 4b ... Electrode 11 ... Insulating ceramic substrate 11a ... Embedded conductive layer 12 ... Filament 14a, 14b ... Electrode

Claims (2)

[Claims] 1. A method for manufacturing a detector having a structure in which a filament is installed in a cell and the resistance value of the filament changes based on the thermal conductivity of a gas flowing in the cell. Is introduced by an ion implantation method to form an embedded dopant layer having a shape corresponding to the filament, and then the semiconductor substrate is etched using a mask having a predetermined pattern to cover the dopant layer with the substrate material. A method for manufacturing a heat conduction detector, characterized in that the above filament is obtained by leaving the filament in the above state. 2. A method of manufacturing a detector having a structure in which a filament is installed in a cell, and the resistance value of the filament changes based on the thermal conductivity of gas flowing in the cell. By implanting ions, a buried conductive layer having a shape corresponding to the filament is formed, and then the insulating substrate is etched using a mask having a predetermined pattern to cover the conductive layer with the substrate material. A method for manufacturing a heat conduction detector, characterized in that the above filament is obtained by leaving the filament in the above state.