CN100576579C - A kind of method for preparing indium column - Google Patents

Abstract

The invention discloses a method for preparing an indium column, which is applied to the preparation process of semiconductor devices and circuits. The method of the present invention includes the process of chip processing, pre-baking, gluing, alignment, exposure, development, film hardening of the positive photolithography process and the process of chip processing, chip loading, vacuuming, evaporation, and chip removal. , The stripped electron beam evaporated indium film and micro-ultrasonic stripping technology, during the glue coating process, a layer of metal film or other dielectric film is prepared in the middle of the positive glue coating, so that the coating becomes a "positive glue thick layer-medium Or metal film-positive photoresist thin layer” structure; then photolithographically pattern the upper layer of thin photoresist, and then wet-etch the dielectric or metal film in the graphic window, and finally remove the bottom layer of thick photoresist by developing method The indium film is peeled off by electron beam evaporation indium film and indium film micro-ultrasonic stripping technology. The accuracy of the shape of the indium column prepared by the technology of the present invention is obviously higher than that of the indium column prepared by the prior art.

Description

A kind of method for preparing indium column

technical field

The invention relates to a semiconductor device and a circuit preparation process, in particular to a detection method for an indium column in a quantum well infrared focal plane detector.

Background technique

Quantum well infrared focal plane detector is a new type of infrared detector developed in recent years. It is the development direction of infrared sensing technology at present. It has the advantages of fast response speed, variable wavelength, thermal stability and good uniformity. Occupying an important position in military and civilian use, it has become a frontier topic of high-tech research that is highly valued internationally.

Infrared focal plane array is the core component of modern infrared imaging system. Its manufacturing process is to prepare the detector and signal processing circuit separately first, and then interconnect them together. The interconnection process usually adopts indium column flip-chip interconnection welding, that is, indium columns with the same pattern are prepared on both the detector chip and the signal processing circuit chip, and then the two indium columns are aligned and welded. To maximize the success rate of interconnection, it is particularly important to prepare high-quality indium pillars, which directly affect the photoelectric performance and imaging quality of focal plane devices.

The currently widely used indium column preparation processes are positive resist photolithography and thermal evaporation coating processes. Positive resist is the most commonly used resist in photolithography. It has good acid resistance and high resolution. Generally, the film thickness does not exceed 2 microns. If the overlay accuracy is not high, the maximum film thickness can be applied in batches. up to 5 microns. However, when the thickness of the indium film increases, because the metal indium is very "sticky", it is very difficult to peel it off by conventional organic solvent heating method, which may easily lead to the dissolution of the photoresist, but the indium film is still stuck on the chip and has not been removed. Generally, the required height of the indium column is 7 microns, and the thickness of the adhesive film is at least 2 microns greater than the height of the indium column, so as to meet the peeling process after the metal coating, that is, the thickness of the adhesive film should be at least 9 microns. A film of such thickness requires special equipment such as a thick glue coating station, exposure machine, etc., so it needs to invest too much cost; especially because the thick glue requires a long development time, when the glue inside the window passes through the development When it is removed cleanly, the geometric dimension of the upper part of the window has also greatly exceeded the design requirements, and its section is in the shape of a washbasin, which cannot form an ideal "scissors' shape", which makes it difficult to peel off and the yield is low. The process flow of the positive resist lithography process is as follows:

Chip processing→pre-baking→glue coating→alignment→exposure→development→film hardening.

Thermal evaporation coating is a method commonly used at home and abroad. The equipment is relatively simple, and the source is heated by a resistance wire, and the evaporation rate is fast; but its disadvantage is that it is uncontrollable, and the indium source used for each evaporation needs to be used up once, so the control of the thickness of the indium film depends entirely on the filling amount of the indium source, which is not easy Precise control of film thickness without pretreatment of the indium source surface. The process flow of thermal evaporation coating is as follows:

Chip processing→mounting→vacuumizing→evaporating→taking out→peeling off.

Contents of the invention

The technical problem to be solved by the present invention is to provide a process method for preparing precise indium column patterns.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

The equipment used in the present invention is an ordinary gluing station and an exposure machine, and the method includes a three-layer stacked positive photolithography process, electron beam evaporation of indium film and micro-ultrasonic stripping technology.

The process flow of the positive resist lithography process is: chip processing→pre-baking→glue coating→alignment→exposure→developing→film hardening; the process flow of evaporation coating is: chip processing→loading→vacuumizing→evaporation coating→taking slice → peel off.

The positive resist photolithography process described in the present invention is a three-layer stacked photolithography technology, that is, when performing the glue coating process, a layer of metal film or other compound medium coating is prepared in the middle of the positive resist coating, so that the coated The layer becomes a three-layer structure of "positive photoresist-dielectric or metal film-positive photoresist"; then the upper layer of thin photoresist is photoetched to make it a precise pattern, and then the medium or medium in the above pattern window is etched away by wet method Metal film, and finally remove the bottom thick glue by developing method. Then electron beams are used to evaporate the indium film, and the indium film is peeled off by micro-ultrasonic stripping technique of indium film.

The further improvement of the above technical solution lies in that the process requirements for the coating of the three-layer superimposed photolithography technology are as follows: the first layer of positive resist is coated with thick glue according to the process requirements, the second layer is 80-200 nanometer dielectric or metal film, and the third layer is The three layers are 400-1000 nanometer positive glue.

The further improvement of the above-mentioned technical solution is that: the above-mentioned medium and metal are medium or metal that do not react with the developer and have certain ductility; wherein the medium is one of silicon nitride and silicon dioxide; the metal film is titanium, platinum , Gold, or a mixture of several.

The electron beam evaporation thick indium film and the micro-ultrasonic stripping technology of the present invention adopt the electron beam evaporation technology to prepare the indium column. Electron beam evaporation can accurately control the evaporation rate and film thickness in real time through the crystal oscillator controller; firstly, pre-evaporation is performed to volatilize the residual oxide layer and impurities on the surface of the indium source; several crucibles on the electron beam evaporation table can evaporate several Metal, so that the contact electrode and indium column are evaporated at one time; the electron beam evaporation uses a planetary rotating fixture to fix the chip, and the evaporation distance from the evaporation source to the chip is greater than 30 cm; using high-vacuum evaporation, start when the vacuum degree reaches 9×10 ^-5 Pa Evaporation procedure, after the evaporation is completed, continue to pump the vacuum to 10 ^-5 Pa and close the high vacuum valve.

After the above process is completed, the chip is taken out, and the indium film is peeled off by micro-ultrasonic stripping technology.

The specific method for peeling off the indium film by the above-mentioned micro-ultrasonic stripping technology is: put the evaporated chip into the heated acetone solution, soak for 30-60 seconds, and when the photoresist expands and is not completely dissolved, the chip is ultrasonicated with low power for 8 ~ 12 seconds, the indium film is cracked, and then the excess metal indium is washed away with a water gun.

Owing to having adopted above-mentioned technical scheme, the technical progress that the present invention obtains is:

The upper layer of thin glue can be photoetched to produce precise patterns, and then the dielectric or metal film in the window is etched away by wet method, and finally the bottom layer of thick glue is developed and cleaned. The key to this technology is to use the characteristics of the medium (such as silicon nitride, silicon dioxide) or metal film (such as titanium, platinum, gold) that do not react with the developer and have a certain stress (ie ductility). Limit the geometric size and shape of the window to form an ideal "scissors' mouth" to facilitate the stripping process after metallization. The application of this dielectric film effectively solves the problem of the collapse of the glue edge of the graphics window caused by the overexposure and development of the thick film in the original photolithography process, resulting in the geometric size of the upper part of the window greatly exceeding the design requirements, and its section is in the shape of a washbasin , unable to form the disadvantage of "scissors' mouth".

The invention adopts the electron beam evaporation technology to prepare the indium column. The electron beam evaporation can precisely control the evaporation rate and film thickness in real time, and can perform pre-evaporation to volatilize the residual oxide layer and impurities on the surface of the indium source, and more effectively The quality of the indium film is guaranteed; and the electron beam evaporation table has several crucibles, which can easily evaporate several metals at one time, that is, the contact electrode and the indium column can be formed by one evaporation, which simplifies the process flow, shortens the process time, and improves the welding accuracy. .

Electron beam evaporation uses a planetary rotating fixture to fix the chip, and the evaporation distance from the evaporation source to the chip is greater than 30 cm, which ensures the verticality and uniformity of evaporation; high-vacuum evaporation is used to ensure that the indium film is not oxidized. The thick indium film is stripped by micro-ultrasonic stripping technology, which ensures that the stripping yield of the indium column is above 95%.

We have taken photos of the appearance of the indium column prepared by the technology of the present invention and the appearance of the indium column prepared by the prior art. After comparing the appearance of the indium column made by the two technologies, it can be seen that the use of The accuracy of the shape of the indium column prepared by the technology of the present invention is obviously higher than that of the indium column prepared by the prior art.

Description of drawings

Fig. 1 is a schematic view of the coating structure of the present invention;

Fig. 2 is the photo of the indium column prepared with prior art;

Fig. 3 is the photo of the indium column prepared by the technology of the present invention;

Fig. 4 is the top view picture of the indium column of the detector photosensitive chip prepared by the technology of the present invention;

Fig. 5 is a top view picture of the indium column of the readout circuit chip prepared by the technology of the present invention.

Detailed ways

Below in conjunction with embodiment the present invention is described in further detail:

The indium column we prepared has the following requirements:

1) The height of the indium column is 7-8 microns, and the thickness of the photoresist film is not less than 10 microns;

2) The photolithographic yield rate is not less than 95%, and the geometric size of the window is ±2 microns from the design value;

3) The uniformity of indium film thickness distribution is ±10% of the design value, and the metal surface is smooth and not oxidized;

4) The indium film has strong adhesion, and the yield of the indium column after peeling off is not less than 95%.

The process flow for preparing the above-mentioned indium column is as follows:

1. Photolithography process

1) Chip treatment: Soak in acetone-isopropanol for several minutes;

2) Pre-baking: 100-180°C, 3 minutes;

3) Apply the first layer of glue: about 10 microns

4) Hardening film: 80～140℃, 1～5 minutes;

5) Deposit metal film or dielectric film: 80-200 nanometers

6) Apply the second layer of glue: 500-1000 nanometers

7) Hardening film: 80～140℃, 1～5 minutes;

8) Counterpoint

9) Exposure

10) One-time development: remove the second layer of glue in the indium column pattern

11) Corrosion: remove the dielectric film in the indium column pattern

12) Second development: remove the first layer of glue in the indium column pattern

2. Indium pillar metallization

1) Chip loading: fix the chip on the planetary fixture in the electron beam evaporation table;

2) Vacuuming and thermal evaporation coating: start the evaporation process when the vacuum degree reaches 9×10 ^-5 Pa;

3) Cooling: After the evaporation is completed, the vacuum is pumped to 10 ^-5 Pa, and then the high vacuum valve is closed;

4) Deflate and take the chip: after cooling, deflate and take out the chip;

5) Stripping: Put the evaporated chip into the heated acetone solution and soak for 30-60 seconds. When the photoresist expands but is not completely dissolved, ultrasonicate the chip with low power for 10 seconds to cause cracks in the indium film, and then Flush off excess indium metal with a water jet.

The glue coating adopts the coating method of "positive glue-medium or metal film-positive glue". After gluing, photolithography is carried out on the upper layer of thin glue to make it into a precise pattern, and then the medium or metal film in the above pattern window is etched away by wet method, and finally the bottom layer of thick glue is removed by developing method. Then electron beams are used to evaporate the indium film, and the indium film is peeled off by micro-ultrasonic stripping technique of indium film.

The specific method of electron beam evaporation coating is: the equipment used for electron beam evaporation of indium film is crystal oscillator controller and electron beam evaporation table, electron beam evaporation adopts planetary rotating fixture to fix chip, and the evaporation distance from evaporation source to chip is more than 30 cm, which ensures the evaporation verticality and uniformity; use high vacuum evaporation, start the evaporation program when the vacuum degree reaches 9×10 ^-5 Pa, and close the high vacuum valve when the vacuum is continued to 10 ^-5 Pa after evaporation; and use indium film micro Ultrasonic stripping technology strips the indium film.

Claims (5)

1, a kind of method for preparing the indium post, comprise that technological process is that the positive resist lithography technology and the technological process of chip processing, preceding baking, gluing, contraposition, exposure, development, post bake is chip processing, load, the electron beam evaporation indium film and the little ultrasonic lift-off technology that vacuumize, evaporate, get sheet, peel off, it is characterized in that: when carrying out positive resist lithography technology coating process, at positive photoresist coating intermediate preparation layer of metal film or other deielectric-coating, make coating become the structure of " positive photoresist thick-layer-medium or metal film-positive photoresist thin layer "; Thin glue with the upper strata is photo-etched into figure then, erodes medium or metal film in the graphical window, removes the thick glue of bottom clean by developing method again; Adopt electron beam evaporation indium film then, and adopt indium film micro-ultrasonic lift-off technology that the indium film is peeled off.

2, a kind of method for preparing the indium post according to claim 1, it is characterized in that described coating process is the positive photoresist of ground floor coating processes required thickness, second layer coating thickness is 80～200 nanometer medium or metal films, and the 3rd layer of coating thickness is the positive photoresist of 400～1000 nanometers.

3, according to claim 1 or 2 described a kind of methods that prepare the indium post, it is characterized in that described medium or metal for not with developer solution reaction and medium or metal with certain ductility; Its medium is the wherein a kind of of silicon nitride, silicon dioxide; Metal film is wherein one or more the mixing of titanium, platinum, gold.

4, a kind of method for preparing the indium post according to claim 1, it is characterized in that described electron beam evaporation indium film device therefor is crystal oscillator controller and electron beam evaporation platform, chip is fixed on the planet rolling clamp, evaporation source greater than 30 centimetres, has guaranteed the up rightness and the uniformity of evaporation to the evaporation of chip distance; Adopt high vacuum evaporation, the second layer glue in the indium post figure is being removed totally, evaporation finishes the back and continues vacuum is evacuated to 10 ^-5Close high vacuum valve during Pa; And adopt the little ultrasonic lift-off technology of indium film that the indium film is peeled off.

5, a kind of method for preparing the indium post according to claim 4, the concrete grammar that it is characterized in that described little ultrasonic lift-off technology is that the chip that evaporation is good is put in the acetone soln that has heated, soaked 30～60 seconds, treat photoresist to expand and when not dissolving fully, chip is used small-power ultrasonic vibration 8～12 seconds, the indium film is cracked, and then water washes away unnecessary indium metal.

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