CN1434500A - Method for measuring tellarium cadmium mercury meterial p-n junction depth - Google Patents

Abstract

This invention dislcoses a p-n junction depth testing method for Te, Cd, Hg material including sample corrosion, conducting type and step hight measurement with the following steps: to corrode and strip the Te, Cd, Hg, sample step by step with corrosion siltion, a measurement of conducting types is processed each corrosion applying temperature difference E.M.F. method which judges if the corrosion arrives the p-n junction based on the theory of the temperature difference E.M.F. of p type semiconductor in opposite direction to that of n type thn to measure the depth of p-n junctino with step testing device.

Description

The method of measurement of mercury cadmium telluride p-n junction junction depth

Technical field

The present invention relates to a kind of method of measurement that is used for the mercury cadmium telluride p-n junction junction depth of Infrared Detectors.

Background technology

The junction depth of p-n junction is a key parameter of preparation semiconductor device, and the method for measurement of junction depth is a lot, such as spreading resistance method, angle lap-stain method, rolled groove method and anode oxidation method etc.But these methods all are not suitable for the measurement of mercury cadmium telluride p-n junction junction depth, and its reason is: a little less than mercury cadmium telluride is highly brittle, and p section bar material particularly, any machining all can make its transoid, thereby people use a stripping layer Hall method usually at present.Stripping layer Hall method is to utilize the just in time opposite characteristic of Hall voltage of p type and n N-type semiconductor N, by repeatedly corroding sample surfaces, every corrosion primary just prepares one-time electrode at sample surfaces, measure one time Hall voltage, anti-phase until the Hall voltage direction, can think this moment to have eroded to the interface, estimate the corrosion depth of mercury cadmium telluride again by corrosion rate, draw junction depth thus.Because this method need thresh electrode, make complicated operation, test process is very long, and corrosion depth is to learn that by the corrosion rate estimation test result is difficult to accomplish accurately.

Technical scheme

Problem based on above-mentioned stripping layer Hall method exists the purpose of this invention is to provide a kind of electrode that need not repeatedly to prepare, and method of measurement is simple, the method for measurement of accurate test result mercury cadmium telluride p-n junction junction depth.

Technical scheme of the present invention is: utilize corrosive liquid that the mercury cadmium telluride sample is corroded one by one, successively peel off, every corrosion primary just carries out the measurement of primary conductive type, and the thermoelectromotive force method is adopted in the measurement of conduction type.Knowledge by semiconductor physics is known, the Fermi level of semi-conducting material moves to intrinsic Fermi level with the rising of temperature, if material spatially has temperature gradient, will cause the gradient of Fermi level in the space, thereby produce electrical potential difference, thermoelectromotive force that Here it is at cold and hot two ends.Under the same conditions, the direction of the thermoelectromotive force of p N-type semiconductor N and n type is opposite.Because when temperature raise, the Fermi level of p type and n N-type semiconductor N was all close to intrinsic Fermi level.Like this, for the Fermi level height in p section bar material hot junction, then the hot junction electromotive force is low; Then opposite fully for n N-type semiconductor N material.Thereby the polarity that just can utilize the thermoelectromotive force at cold and hot two ends is judged the conduction type of semi-conducting material.When test, find potential inversion, show the position that erodes to p-n junction, utilize the step instrument just can record the junction depth of p-n junction.

Concrete steps of the present invention are as follows:

A. the preparation of sample

Part surface growth one deck SiO at sample ₂Diaphragm is seen Fig. 1.

B. the measurement of substep corrosion and conduction type

The sample that will have the part diaphragm is put into the mixed liquor of bromine and ethanol, and its volume ratio is 1: 50～200, and the temperature maintenance of corrosive liquid is in freezing point, and corrosion rate is 0.01 μ m/s-0.1 μ m/s.For the first time etching time can highly be controlled according to institute's test sample product p-n junction estimation, shortens one by one later on, during particularly near interface, etching time is shortened to make in the measure error scope 0.1 μ m of p-n junction junction depth permission.

Every corrosion primary is just surveyed the conduction type of a mercury cadmium telluride sample, to judge whether to arrive the interface.For mercury cadmium telluride, since its near room temperature just near intrinsic excitation, for guaranteeing the accurate of test result, measurement is carried out under liquid nitrogen temperature, be about to a probe cooled with liquid nitrogen of sample and universal instrument, another root probe maintenance room temperature is when sample and cold probe are cooled to liquid nitrogen temperature, simultaneously cold and hot two probes are pressed in lightly the position of the corrosion of sample respectively, write down the positive and negative of universal instrument reading.After the corrosion and test through several times repeatedly, the reading of universal instrument occurs by just changeing negative or turning negative number to positive number, and this has been corroded to the interface with regard to illustrative material.Said universal instrument is common digital, and it is just passable to have a milliampere level range.

C. shoulder height test

Before the height of scaffold tower rank, the diaphragm of sample is removed, expose the initial surface that is not corroded, form the step that height is a junction depth, measure shoulder height with the step instrument.

Description of drawings

Fig. 1 is sample part surface growth SiO ₂The cross-sectional view of diaphragm;

Fig. 2 is a sample conduction type instrumentation plan;

The p-n junction junction depth figure of Fig. 3 for recording with the inventive method.

Embodiment

Below the specific embodiment of the present invention is elaborated:

1.SiO ₂The growth of diaphragm: in order to form the step of a true reflection p-n junction junction depth, we need a sample part to be corroded, and another part is not corroded.Like this, when the part that is corroded was exposed the knot face because of progressively corroding, this knot face formed a step with the initial surface of the part that is not corroded.Clearly, the height of this step is exactly the junction depth of p-n junction.Introduce its growth step below:

A. sample cleans: cleaned 20 minutes down at 65 ℃ with trichloroethylene earlier, cleaned 20 minutes down at 65 ℃ with ether then, soaked 15 minutes in the acetone of 65 ℃ of constant temperature and ethanol.It is pure that above reagent is analysis, and the sample after cleaning surface-brightening is clean.

B. resist coating is protected at the part resist coating that sample need corrode, and the part that does not need to corrode then is exposed in the sputtering atmosphere, carries out SiO ₂Sputter, SiO ₂Thickness for being not less than 0.1 μ m.Sputter finishes, and need corrode the top photoresist of part to sample together with the SiO above it with acetone ₂Together remove.

2. the measurement of substep corrosion and conduction type: the preparation of corrosive liquid has two principles, and the one, corrosive liquid should be rare as far as possible, to reduce corrosion rate; The 2nd, make corrosive liquid can be good at control every the corrosion rate of mercury for tellurium.Like this, by the control corrosion rate, each etching time makes tellurium carry out with a very little step-length every the corrosion of mercury.According to these two principles, the inventor recommend volume ratio be the mixed liquor of 1: 100 bromine and ethanol as corrosive liquid, the corrosive liquid temperature remains on freezing point.General height according to the p-n junction of growth sample estimation is 1 μ m, for the first time etching time can be controlled in 10s, shortens one by one later on, during particularly near interface, etching time can be controlled in 1s-2s, can make tellurium like this in the error range 0.1 μ m of corrosion with the permission of measurement thickness of mercury.

Every corrosion primary is just surveyed the conduction type of a mercury cadmium telluride sample, to judge whether to arrive the interface.Measurement is carried out under liquid nitrogen temperature, be about to a probe cooled with liquid nitrogen of sample and universal instrument, another root probe keeps room temperature, when sample and cold probe are cooled to liquid nitrogen temperature, while is pressed in cold probe 1 and thermal probe 2 position 3 of the corrosion of sample respectively lightly, write down the positive and negative of universal instrument 4 readings, see Fig. 2.After the corrosion and test through several times repeatedly, the reading of universal instrument occurs by just changeing negative or turning negative number to positive number, and this has been corroded to the interface with regard to illustrative material.

3. shoulder height test

Before the height of scaffold tower rank; sample is dipped in several seconds in the hydrofluoric acid solution; remove the diaphragm of sample; expose the initial surface that is not corroded; form the step that height is a junction depth; can conveniently measure the height of step with the DEKTAK3 surface profile measuring system step instrument of Veeco company, its measurement result is seen Fig. 3.

Claims (1)

1. the method for measurement of a mercury cadmium telluride p-n junction junction depth comprises the growth of sample diaphragm, the measurement of burn into conduction type, it is characterized in that concrete steps are as follows:

A. the preparation of sample

Part surface growth one deck SiO at sample ₂Diaphragm;

B. substep corrodes and the step measurement conduction type

To have SiO ₂The sample of diaphragm is put into the mixed liquor of bromine and ethanol, its volume ratio is 1: 50～200, the temperature maintenance of corrosive liquid is in freezing point, corrosion rate is 0.01 μ m/s-0.1 μ m/s, etching time can be controlled according to the p-n junction junction depth of institute's test sample product estimation and the concentration of corrosive liquid for the first time, shorten one by one later on, during particularly near interface, etching time is shortened to the p-n junction junction depth is measured in the error range 0.1 μ m that allows;

Every corrosion primary is just surveyed the conduction type of a sample, to judge whether to arrive the interface, measurement is carried out under liquid nitrogen temperature, be about to a probe cooled with liquid nitrogen of sample and universal instrument, another root probe keeps room temperature, when sample and cold probe are cooled to liquid nitrogen temperature, while is pressed in cold probe (1) and thermal probe (2) position (3) of the corrosion of sample respectively lightly, write down the positive and negative of universal instrument (4) reading, after the corrosion and test of sample through several times repeatedly, the reading of universal instrument occurs by just changeing negative or turning negative number to positive number, and this has been corroded to the interface with regard to illustrative material; Said universal instrument is common digital, and it is just passable to have a milliampere level range;

C. shoulder height test

Before the height of scaffold tower rank, the diaphragm of sample is removed, expose the initial surface that is not corroded, form the step that height is a junction depth, measure shoulder height with the step instrument.

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