JPS62197720A - Manufacture of color identifying element - Google Patents

Abstract

PURPOSE:To obtain an element free from deterioration or the like in spectral characteristics even when the filling rate of MgF2 film is about 0.7, by executing a vacuum baking before a can sealing to form a film at a normal temperature. CONSTITUTION:First, a photodiode is formed on an Si wafer and a interference filter 2 comprising a multilayer film made up of a Ag and MgF2 is formed on a light receiving surface of the photodiode by vacuum evaporation. Then, this wafer is taken out into outside air divided into one-chip units. Then, one chip element 1 is dye bonded on a stem 6 by a conducting paste or the like and an electrode on the chip 1 is connected to an electrode on the stem 6 by wire bonding using Au wire or the like. The stem 6 is sent into a vacuum baking furnace 11. Then, a door 1a following a sealing chamber 12 of the vacuum baking furnace 11 is opened to send the stem carrying the chip, a cap and the like to the sealing chamber 12 where a can sealing is done. After the sealing, the completed element is taken outside from a take-off port 13.

Description

[Detailed Description of the Invention] Summary of the Invention In the manufacturing process of a color identification element, by performing vacuum baking before CanSeal, it is possible to transfer to CanSeal with moisture adsorbed during the previous process removed. can. As a result, 2 the reproducibility of spectral characteristics is improved, 1 and a color discrimination element with little change over time can be obtained.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a color identification element used to identify the color of a color recognition object.

A conventional color discrimination element usually includes a stem, an element chip fixed to the stem 1-, a cap fixed to the stem, and an incident light window for allowing light to enter the light-receiving surface of the element chip. It is equipped with An element chip generally includes one or more light-receiving elements (photodiodes) formed on a semiconductor substrate, and an optical filter formed on these light-receiving elements and having different spectral transmission characteristics for incident light. It is equipped with This optical filter is an interference filter, and is composed of a multilayer film in which metal films and dielectric films are alternately laminated.The metal film is made of Ag, which has no absorption in the visible region, or the dielectric is made of a desired material. MgF2 with a low refractive index was selected so that the spectral transmission characteristics could be designed.

As shown in FIG. 5, such a color discrimination element is produced by depositing an interference filter on a substrate having a light receiving element, and then dividing the substrate into chips.

The chip is die-bonded onto the stem, the wiring is wire bonded, and finally a cap with a window for incident light is can-sealed to the stem.

Now, MgF2 of the top layer in the multilayer film of the above interference filter
The main purpose of this is to protect the underlying Ag film. However, when a 9M g F 2 film is formed at room temperature,
Since the filling factor is about 0.7, moisture in the air is adsorbed immediately after being taken out from the vacuum evaporation apparatus. M of interference filter
Since the gF2 membrane is can-sealed while adsorbing moisture, the following problems have arisen.

(1) The apparent refractive index of the M g F 2 film changes due to the presence of adsorbed water, resulting in poor reproducibility of 1-spectral characteristics.

(2) The adsorbed water oxidizes the Ag film over time, resulting in a decrease in optical discrimination ability.

(3) Adsorption and desorption of water is repeated within the camp due to changes in ambient temperature, and the 2-spectral characteristics change each time.

The above-mentioned filling rate refers to the following concept. In general, when III is formed into a film by vacuum evaporation method etc., when viewed microscopically, it looks like a column (
The crystals grow in the form of columns, with voids between the columns.

The filling factor refers to the ratio of the volume of the crystal pillars to the total thin film volume, which is obtained by subtracting the voids from the total thin film volume. Therefore, the closer the filling factor is to 1, the denser the thin film is, and the closer the filling factor is to 0, the coarser it is. The filling rate is expressed by the following formula.

(Filling rate) - [(Total volume of thin film) - (Void) / (Total volume of thin film) - (Volume of crystal pillars) / (Total volume of thin film) MgF2 at a high substrate temperature of 200°C or higher When a film is formed, the filling factor approaches 1, and changes in characteristics can be prevented.

However, when the temperature is raised, the Ag metal film rearranges, which causes a problem in that the spectral characteristics of the interference filter change.

Invention lI! E. Purpose of the Invention The present invention provides a method for manufacturing a color discrimination element, which does not cause deterioration of spectral characteristics even when the MgF2 film is formed at room temperature and has a filling rate of about 0.7. I take this to heart.

Structure and Effects of the Invention The present invention fixes an element chip on a stem and performs necessary wiring, and then covers the stem with a cap having a window for incident light to seal the color identification element. Immediately before the sealing process with the cap, the device chip on the stem is subjected to a vacuum baking process, and then the sealing process is performed without exposing the stem and the device chip to the atmosphere. .

Immediately before can-sealing, a vacuum baking process is performed to remove moisture adsorbed during the manufacturing process from the element chip, etc., so that the element chip is can-sealed in a dry state. Therefore, M
The refractive index of the gF2 film is constant and the reproducibility of the 2-spectral characteristics is good.Since it does not contain water, there is no oxidation of the Ag film, so there is little change in color discrimination ability over time, and there is also little temperature change in the 1-spectral characteristics. is obtained.

This invention is applicable not only to a color discrimination element in which a plurality of light receiving elements are provided on a chip and an interference filter having mutually holed spectral characteristics is formed on these light receiving elements; Needless to say, the present invention can also be applied to a monochromatic element in which an interference filter having a passband of a specific wavelength is formed on the light receiving element.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows (1-manufacturing) of a manufactured color identification element. The Si chip 1 is provided with several photodiodes as light receiving elements, and these photodiodes Interference filters 2 having mutually different spectral transmission characteristics are formed on the light receiving surface of the chip 1. Such a chip 1 is conductively fixed on a stem 6, and the terminals of each photodiode are provided on the stem 6. Wire bonding is made to the terminals (the wires are indicated by 4).The stem 6 carrying the chip 1 is then provided with a cap 5 having a window, i.e. a glass window 3, through which incident light passes.

Can-sealed.

Such a color identification element is manufactured by the steps shown in FIG.

First, a photodiode is formed on the S1 wafer, and an interference filter made of a multilayer film of Ag and MgF2 is formed on the light receiving surface of the photodiode by vacuum evaporation.

This wafer is taken out into the atmosphere and pre-kneaded into one chip at a time. In other words, divide.

The one-chip element 1 is die-bonded onto the stem 6 using a conductive paste or the like, and the electrodes on the chip 1 are connected to the electrodes of the stem 67 by wire bonding using Au wire or the like.

After this, the stem 6 carrying the chip 1 is sent to a vacuum baking process together with the cap 5 that can be placed on the stem 6 if necessary. As shown in FIG. 3, a vacuum baking process is a process in which a vacuum baking furnace 11 is evacuated by a vacuum device 14, the temperature is raised to an appropriate temperature by a heater 15 in the furnace 11, and a stem introduced into the furnace 11 is heated to an appropriate temperature. This is a process to remove N20 and other gases adsorbed on the tip on the stem, the interference filter of the tip, the cap, etc. After this vacuum baking process, N2 gas is introduced into the vacuum baking furnace 11 to return it to normal pressure. The vacuum baking conditions are, for example, a degree of vacuum of 10-ITorr, a temperature of 150'C, and a time of 90 minutes.

A hermetic seal chamber 12 is directly connected to the vacuum baking furnace 11, and the inside of this chamber 12 is also maintained in an N2 gas atmosphere. Door 1 leading to seal chamber 12 of vacuum baking furnace 11
By opening 1a, the stem, cap, etc. on which the chip is mounted are sent to the sealing chamber 12, where they are sealed. That is, the cap 5 is placed on the stem 6 and sealed by electric welding. After this sealing, the completed color identification element is taken out from the exit port 13.

In this way, the sample is always kept in N2 gas from the vacuum baking oven to the hermetic seal chamber.

Since it is not exposed to the atmosphere and H, O, etc. are removed by vacuum baking, H20 etc. will no longer adhere to the chip etc. inside the cap of the color identification element.

FIG. 4 shows a comparison of photocurrent changes over time between a color discrimination element manufactured by the above-described method and a color discrimination element manufactured by a conventional method. The characteristics indicated by A are the characteristics of the device subjected to the vacuum baking process according to the manufacturing method of the present invention, and the characteristics shown by B are the characteristics of the conventional device not subjected to the vacuum baking process. As is clear from this graph, the changes over time in the characteristics of the color discrimination element manufactured by the method of the present invention are extremely small, and the reliability is very low.

[Brief explanation of drawings]

Figure 1 is a flow chart showing the manufacturing process of a color identification element according to the present invention, Figure 2 is a sectional view showing the structure of the manufactured color identification element, and Figure 3 is a diagram showing a vacuum baking furnace and a hermetic seal chamber. FIG. 4 is a graph showing a comparison of photocurrent changes over time between a color discrimination element manufactured by the method of the present invention and an element manufactured by a conventional method. FIG. 5 is a flow chart showing a conventional manufacturing process. 1...Si chip, 2...Interference filter. 3...Glass window, 4...Wire. 5...Cap, 6...Stem. 11...Vacuum baking oven. 12...Hermetic seal chamber. that's all

Claims (1)

[Scope of Claims] A color identification element is manufactured by fixing an element chip on a stem and performing necessary wiring, and then covering and sealing the stem with a cap having a window for incident light. Immediately before the sealing process with the cap, the element chip on the stem is subjected to a vacuum baking process, and then the sealing process is carried out without exposing the stem and the element chip to the atmosphere. Method of manufacturing elements.