JPH0283948A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To produce a highly reliable semiconductor element by adjusting power supply so that the sum of absolute value of a gate voltage and a drain voltage may be less than the gate breakdown voltage and also in pinch-off state, measuring drain current, and detecting defects. CONSTITUTION:A gate power supply EG and a drain power supply ED are adjusted to form a depletion layer 3 at a channel layer 2, thus resulting in a pinch-off state. Then, voltage where the sum of absolute value of a gate voltage and a drain voltage does not exceed the gate breakdown voltage is applied to. At this time, if there is any defect within the gate electrode G, no layer 3 is formed at a layer 2 opposing it and a drain current I flows through the layer 2 where no high-density layer 4 and layer 3 exist. When this current I is measured and the value exceeds the specified value, it is judged that there is defect in the electrode G. It allows defect of gate electrode of a multilayer film which cannot be detected by optical means to be detected, thus producing a highly reliable semiconductor element.

Description

[Detailed Description of the Invention] [Summary] Method for manufacturing semiconductor devices, especially compound semiconductor MESFET
Regarding the manufacturing method, for the purpose of detecting defects in the gate electrode of the compound semiconductor MESFET, one electrode of a variable voltage gate power source is connected to the gate electrode, the other electrode of the gate power source is connected to the source electrode, and An electric circuit is constructed in which a current measuring means is connected to the other electrode of a variable voltage drain power supply connected to the drain electrode with a polarity opposite to that of the gate electrode voltage, and the absolute value of the voltage value of the gate power supply is The gate power supply and drain power supply are adjusted so that the sum of the absolute values of the voltage values of the drain power supply does not exceed the gate breakdown voltage value of the MESFET, and the MESFET is in a pinch-off state.
The current value of the drain current flowing between the source electrode and the drain electrode of ET is measured by the current measuring means to detect a defect in the gate electrode.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a compound semiconductor MESFET.

[Conventional technology]

Conventionally, for example, gate electrodes of GaAs MESFETs have often been made of single-layer films formed by vacuum-depositing only AI (aluminum) as shown in FIG.

This is because AI has many advantages such as low resistivity, excellent bonding properties, easy patterning, low price, and easy availability.

However, A7 electrodes have drawbacks such as poor corrosion resistance and easy electromigration, so they are used in some GaAs MES F [", T
Physically and chemically stable titanium (Ti) is used for electrodes such as
), platinum (Pt), gold (Au>, etc.) by vacuum evaporation, and there is a growing tendency to adopt electrodes made of multilayer films as shown in FIG. 6.

[Problem to be solved by the invention]

GaAs MESF using electrodes composed of the above multilayer films
A problem with ET is that visual inspection using optical means such as a microscope cannot be performed sufficiently at the wafer processing stage.

That is, defects 5 in the gate electrode G formed of a single layer film as shown in FIG. 7 showing a cross section taken along line bb in FIG. 5 can be easily detected by using optical means such as a microscope.

However, although the surface electrode G2 of the gate electrode G composed of a multilayer film as shown in FIG.
If there is a defect 5 in the internal electrode Gl that is in close contact with the channel layer 2, as shown in FIG. 8, the cross section taken along the line c--c in the figure cannot be detected by the above-mentioned optical means.

In particular, it is not uncommon for recent GaAs MESFETs to have gate lengths of around 1 μm in order to speed up switching times and the like.

Therefore, even a slight defect 5 in the gate electrode G can cause the MESFET to
The problem of increasing the possibility of deteriorating the reliability and electrical characteristics of electronic devices is attracting attention.

Therefore, the present invention provides a manufacturing method that can detect defects 5 in the internal electrode G1 of the gate electrode G of the MESFE'r made of a multilayer film of metal that cannot be detected even by using optical means such as a microscope. It has been done.

[Means to solve the problem]

FIG. 1 is an explanatory diagram of the principle for detecting defects in the gate electrode of the GaAs MESFET, in which one electrode of a voltage-variable gate electrode #EG is connected to the gate electrode G, and the other electrode of the gate power source EG is connected to the gate electrode G. An electric circuit is connected to the other electrode of a variable voltage drain electrode aED connected to the source electrode S and to the drain electrode with a polarity opposite to the voltage of the gate electrode G, with a current measuring means A interposed therebetween. so that the sum of the absolute value of the voltage value of the gate voltage tJEG and the absolute value of the voltage value of the drain power supply ED does not exceed the gate breakdown voltage value of the MESFET, and MESFET
The gate power supply EG is turned on so that T is in a pinch-off state.
and the drain power supply ED are adjusted, and the current value of the drain current l flowing between the source electrode S and the drain electrode of the MESFET is measured by a current measuring means A, for example, an ammeter.

[For production]

As shown above, the gate power supply EG and drain power supply E in Figure 1
D is adjusted to form a depletion N3 in which no conductive carriers exist in the channel layer 2 of the MESFET, and the MBs
When the FET is put into a pinch-off state, the current value of the drain current ■ will be at most a few μ if there is no defect 5 in the internal electrode Gi formed inside the surface electrode G2 of the gate electrode G as shown in FIG. It is.

However, when the same voltage is applied as when there is no defect, if there is a defect 5 in the internal electrode Gl, in the a-a cross section of FIG. Since the depletion layer 3 is not formed in the drain current 1, the drain current 1 flows by about 1 to 5 mA via the high concentration layer 4 and the channel layer 2 in which the depletion layer 3 is not formed.

Therefore, the drain current I is measured with an ammeter A, and the current value of the train current I exceeds 100 tt A ~ IESF
By detecting ET, it becomes almost possible to detect the defect 5 in the internal electrode Gl of the gate electrode [j.

Note that the sum of the absolute value of the voltage value of the gate power supply and the absolute value of the voltage value of the input/input power supply does not exceed the gate breakdown voltage value because the voltage exceeding the gate breakdown voltage value is not applied to the gate electrode. This is because if applied between the drain electrodes, a minute current will flow from the channel layer to the gate electrode regardless of the presence or absence of defects, making it impossible to determine the presence or absence of defects by measuring the drain current.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to FIG. 3.
E T has a width Y of the gate electrode G of 10 μm, a length X of the gate electrode G of 1 μm, and Ti, Pt, and Au in this order.
About 500 people oxidize P (about 2000 people oxidize U 2 μm)
After vacuum-depositing the film to a certain thickness, the deposited film was removed by F-Q, leaving only the required area.

The above GaAsMF as shown in FIG.
A circuit is constructed to measure the relationship between the gate electrode defect width W in the pinch-off state and the drain current ■, and the gate power source EG
FIG. 4 shows the results of measuring the drain current (2) using the gate electrode defect width W as a parameter by adjusting the voltage value of 14 volts and the voltage values of the drain voltage 'tJ and ED to 3 volts.

Based on the above results, in Fig. 3, the voltage value of the gate power supply EG is set to 14 volts, the voltage value of the drain voltage aED is set to 3 volts, and the drain current I exceeds )OOμA.
By selecting the ESFETs, defects 5 in the internal electrode Gl of the gate electrode G can be detected.

In addition, the above example is G a As M E S F E T
However, it is obvious that the present invention can be applied to other compound semiconductor MESFETs having gate electrodes made of multilayer films.

〔Effect of the invention〕

As explained above, according to the present invention, MESFETs that cannot be detected by visible inspection using optical means such as a microscope
It is possible to provide a method of manufacturing a semiconductor device that allows defects in a gate electrode formed of a multilayer film to be detected using an extremely simple method, thereby improving the electrical characteristics and reliability of a MESFET.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the principle of the present invention. Figure 2 is an a-a line schematically showing a state in which there is a defect in the K'-1 electrode made from a multilayer film of pinch-off type 〇FE, 'F. 3 is a schematic diagram for explaining one embodiment of the present invention. FIG. 4 is a diagram of actual measurement data showing the relationship between gate electrode defect W and drain current measured in one embodiment of the present invention. Figure 6 is a cross-sectional side view of the main part showing a MESFET with a single-layer film electrode, Figure 6 is a side cross-sectional view of the main part showing a MESFET with multiple till electrodes, and Figure 7 is a schematic diagram showing gate electrode defects made from a single-layer film. FIG. 8 is a sectional view taken along line cc, schematically showing defects in the gate electrode formed from the multilayer film. In the figure, 1 is a GaAs substrate, 2 is a channel layer, 3 is a depletion layer, 4 is a high-resolution layer, 5 is a gate electrode defect, G is a gate electrode, G1 is an internal electrode, G2 is a surface electrode, and S is a surface electrode. The source electrode, D is the drain electrode, A is the ammeter, ■ is the drain current, EG is the gate power supply, and IED is the drain power supply. V! Air tuna off payment F! , FET me 494#'lg n kate foundation? 41 Nogu crouching hired crocodile ゛ε hair ＼ J door wa L Nio, fa-a humble tC horizon b unk 2nd figure fig.

Claims (1)

[Claims] A method for detecting defects in a gate electrode of a compound semiconductor MESFET, comprising: connecting one electrode of a variable voltage gate power source (EG) to the gate electrode (G); is connected to the source electrode (S), and the other electrode of a variable voltage drain power source (ED) connected to the drain electrode (D) with a polarity opposite to the voltage of the gate electrode (G). , constitutes an electric circuit connected with a current measuring means (A) interposed therebetween, and the sum of the absolute value of the voltage value of the gate power supply (EG) and the absolute value of the voltage value of the drain power supply (ED) is the sum of the absolute value of the voltage value of the drain power supply (ED). without exceeding the gate breakdown voltage value and the above MESF
The gate power supply (
EG) and the drain power supply (ED) to obtain the ME
The source electrode (S) and the drain electrode (D) of SFET
A method for manufacturing a semiconductor device, characterized in that defects in the gate electrode (G) are detected by measuring the current value of a drain current (I) flowing between the gate electrodes (I) using the current measuring means (A).