KR20010073400A - an electrode for breakdown voltage measurement of silicon on insulator wafer and a measurement method thereof - Google Patents

Abstract

PURPOSE: An electrode for measuring an insulation breakdown voltage of a silicon double film wafer is provided to reduce the number of manufacturing processes by forming the electrode for measuring an insulation breakdown voltage without an ion injection and diffusion process. CONSTITUTION: An insulating oxide film(302) is formed thickly on the bottom layer(301) of a silicon substrate, and a silicon thin film(303) is formed on the insulating film(302). A field oxide film(304) is formed on the bottom layer(301) to separate the silicon thin film(303) into a plurality of isolating region. A gate insulating film(314) is formed on the silicon thin film(303), and a gate electrode(306), a source electrode(305) and a drain electrode(307) is formed on the gate insulating film(314). The source electrode(305) and the drain electrode(307) are connected to the silicon thin film(303) via a contact hole formed on the gate insulating film(314). The silicon thin film(303) is doped or not doped in each isolating region by one kind of impurity of a p-type impurity and an n-type impurity.

Description

An electrode for breakdown voltage measurement of silicon on insulator wafer and a measurement method

The present invention relates to an electrode for measuring the dielectric breakdown voltage of a silicon double layer wafer, and more particularly, to an electrode structure that can be used for measuring the dielectric breakdown voltage of a gate insulating film for quality evaluation of a silicon double layer wafer.

Next, the structure of the dielectric breakdown voltage measuring electrode according to the related art will be described with reference to the accompanying drawings.

1 is a cross-sectional view of an electrode for dielectric breakdown voltage measurement of a silicon single film wafer.

The gate insulating film 102 is formed on the silicon substrate 101, and the electrode 103 for insulating breakdown voltage measurement is formed on the gate insulating film 102. A conductive line 105 connected to a measuring instrument (not shown) is connected to the lower surface of the substrate 101, and a probe 104 connected to the measuring instrument 103 is in contact with the measuring electrode 103.

In the dielectric breakdown voltage measuring electrode having such a structure, a voltage difference is applied between the measuring electrode 103 and the silicon substrate 101 through the probe 104 and the conductive wire 105 to cause dielectric breakdown of the gate insulating film 102. Measure the voltage difference.

However, in the case of a silicon double film wafer in which a thick oxide film is formed inside the wafer to electrically insulate the front and back surfaces of the wafer to obtain electrical stability of the device, the structure of the dielectric breakdown voltage of the gate insulating film cannot be measured with the structure shown in FIG. 1. Do. In this case, a metal oxide field effect transistor (MOSFET) is formed to measure the dielectric breakdown voltage.

FIG. 2 is a cross-sectional view of an electrode for dielectric breakdown voltage measurement of a silicon double layer wafer according to the related art, and FIG. 3 is a view illustrating a shape of an electric field formed during the dielectric breakdown voltage measurement in the electrode structure for dielectric breakdown voltage measurement of FIG. 2. Drawing.

An insulating oxide film 202 is formed on the silicon substrate base layer 201, and a silicon thin film 203 is formed on the insulating oxide film 202. The silicon thin film 203 is formed with a source region 212 and a drain region 213 heavily doped with N-type or P-type impurities, and are adjacent to each other around the source region 212 and the drain region 213. An isolated oxide film (field oxide) 204 is formed to separate the oxides. A gate insulating film 214 is formed on the silicon thin film 203, and a gate electrode 206, a source electrode 205, and a drain electrode 207 are formed on the gate insulating film 214. At this time, the source electrode 205 and the drain electrode 207 are connected to the source region 212 and the drain region 213 through contact holes formed in the gate insulating film 214, respectively.

The probe of the instrument is brought into contact with the gate electrode 206, the source electrode 205, and the drain electrode 207 of the MOSFET having such a structure, and the gate is connected to the lower surface of the substrate base layer 201 with a conductor connected to the instrument. By applying a voltage difference between the electrode 206 and the source electrode 205 or between the gate electrode 206 and the drain electrode 207 and gradually increasing the voltage difference until the gate insulating film 214 loses the insulating function. The dielectric breakdown voltage of the gate insulating film 214 is measured.

The electric field formed during the dielectric breakdown voltage measurement is concentrated between the bottom surface of the gate electrode 206 and the side close to the gate electrode 206 of the source region 213 and the drain region 212, as shown in FIG. 3. .

However, in order to form the MOSFET, a plurality of processes, such as impurity implantation and impurity diffusion, must be added to form the source and drain regions 212 and 213.

The technical problem to be achieved by the present invention is to reduce the number of manufacturing processes by simplifying the electrode structure for measuring the dielectric breakdown voltage of the silicon double film wafer.

1 is a cross-sectional view of an electrode for measuring dielectric breakdown voltage of a silicon single film wafer;

2 is a cross-sectional view of an electrode for dielectric breakdown voltage measurement of a silicon double film wafer according to the prior art;

3 is a view showing the shape of the electric field formed during the measurement of the breakdown voltage in the electrode breakdown voltage measurement electrode structure of FIG.

4 is a layout view of an electrode for dielectric breakdown voltage measurement of a silicon double film wafer according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view taken along the line VV ′ of FIG. 4;

FIG. 6 is a view showing the shape of an electric field formed when the dielectric breakdown voltage is measured in the electrode breakdown voltage measuring electrode structure of FIG. 5;

7 is a graph showing the amount of current flowing through each electrode when measuring the breakdown voltage in the electrode breakdown voltage measurement electrode structure according to an embodiment of the present invention,

8 is a cross-sectional view when an electrode breakdown voltage measurement electrode structure according to an embodiment of the present invention is applied to a silicon single film wafer;

FIG. 9 is a graph showing the amount of current flowing through each electrode in the dielectric breakdown voltage measurement in the electrode structure of FIG. 8;

FIG. 10 is a graph comparing only the gate current of FIGS. 7 and 9.

In order to solve this problem, the present invention forms an electrode for dielectric breakdown voltage measurement of a silicon double film wafer having no source and drain regions in the silicon thin film.

Specifically, an insulating oxide film is formed on the silicon base substrate, a silicon thin film is formed on the insulating oxide film, and a gate insulating film having a contact hole for exposing the silicon thin film is formed on the silicon thin film. A gate electrode is formed on the gate insulating film, and a source electrode and a drain electrode connected to the silicon thin film are formed on the gate insulating film through contact holes, respectively, and an isolated oxide film is formed to separate the silicon thin film into a plurality of isolated regions. have. Here, each isolated region of the silicon thin film is doped with one or less kinds of impurities.

Next, the structure of the dielectric breakdown voltage measuring electrode according to the exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

4 is a layout view of an electrode for dielectric breakdown voltage measurement of a silicon double film wafer according to an exemplary embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along line VV ′ of FIG. 4.

The insulating oxide film 302 is formed thick on the silicon substrate base layer 301, and the silicon thin film 303 is formed on the insulating oxide film 302. At this time, the thickness of the insulating oxide film 302 is about 360 nm and the thickness of the silicon thin film 303 is about 190 nm. On the silicon substrate base layer 301, a field oxide 304 is formed which separates the silicon thin film 303 into a plurality of isolated regions. A gate insulating film 314 is formed on the silicon thin film 303, and a gate electrode 306, a source electrode 305, and a drain electrode 307 are formed on the gate insulating film 314. At this time, the source electrode 305 and the drain electrode 307 are connected to the silicon thin film 303 through a contact hole formed in the gate insulating film 314, respectively, and the silicon thin film 303 is an isolated oxide film ( Each region isolated by 304 is doped with or not doped with either type of N or P type impurities. That is, no source region or drain region is formed separately. Here, the thickness of the gate insulating film 314 is about 18 nm.

If the electrode structure for dielectric breakdown measurement is formed in this way, processes such as ion implantation and diffusion for forming source and drain regions can be omitted.

The probe of the measuring instrument is brought into contact with the gate electrode 309, the source electrode 305, and the drain electrode 307 of the electrode structure for measuring an insulation breakdown voltage having such a structure, and is connected to the measuring instrument on the lower surface of the substrate base layer 301. Is applied, a voltage difference is applied between the gate electrode 309 and the source electrode 305 or between the gate electrode 309 and the drain electrode 307, and the gate insulating film 314 loses its insulation function. The dielectric breakdown voltage of the gate insulating film 314 is measured by gradually increasing it until

As shown in FIG. 6, the electric field formed during the dielectric breakdown voltage measurement is formed between the gate electrode 306, the source electrode 305, and the drain electrode 307.

7 is a graph showing the amount of current flowing through each electrode when measuring the breakdown voltage in the electrode breakdown voltage measurement electrode structure according to an embodiment of the present invention.

An insulation breakdown voltage measuring electrode having a structure as shown in FIG. 5 was formed on a 6-inch silicon double film wafer, and the dielectric breakdown voltage was measured while the instruments were connected using the probes 308, 309, and 310. . At this time, the source, drain, and base voltages were fixed, and the gate voltage was changed at 0.4V intervals from 0V to -40V.

Insulation breakdown of the gate insulating film 314 can be observed in that the gate current rapidly increases when the gate voltage reaches -35V. That is, the gate current rapidly increases when the gate voltage reaches -35V through a tunneling state in which the insulation state is maintained until the gate voltage reaches about -27V, and the gate current falls below the gate voltage, and the gate current increases with a constant slope. Thus, dielectric breakdown of the gate insulating film 314 occurs.

The current entering the gate electrode 306 is divided into a source and a drain 305 and 310, which can be seen that the sum of the measured source current and the drain current is almost equal to the gate current. The base current connected to the substrate base layer 301 under the insulating oxide 302 hardly changes at very low levels, meaning that the electric field is not dispersed below the insulating oxide 302.

However, the dielectric breakdown voltage measured according to the embodiment of the present invention may not be an accurate dielectric breakdown voltage of the gate insulating film. This is because the electric field formed during the dielectric breakdown voltage measurement is not perpendicular to the gate insulating layer 314 as shown in FIG. 6. Therefore, to obtain more accurate dielectric breakdown voltage, correction of measured value is needed. The correction method for the measured value will now be described.

FIG. 8 is a cross-sectional view of an electrode structure for measuring breakdown voltage according to an embodiment of the present invention applied to a silicon single film wafer. FIG.

A gate insulating film 414 is formed on the silicon substrate 401, and a gate electrode 406, a source electrode 405, and a drain electrode 407 are formed on the gate insulating film 414. An isolation oxide film 411 is formed on the silicon substrate 401 to separate the substrate 401 into a plurality of device regions, and a base electrode 411 is formed on the bottom surface of the substrate 401. At this time, the thickness of the gate insulating film 414 is formed to be 18 nm as in FIG.

Here, while the source electrode 405, the drain electrode 407, and the base electrode 406 are fixed at 0V, the gate voltage is varied from 0V to -40V at 0.4V intervals. Then, a current change graph as shown in FIG. 9 is obtained.

9, the base current curve almost overlaps the gate current curve in the entire range of the gate voltage VG. This means that the electric field due to the gate voltage is concentrated between the gate electrode 406 and the base electrode 411. That is, as shown in FIG. 8, the electric field is formed substantially perpendicular to the gate insulating layer 414. Therefore, it can be seen that the dielectric breakdown voltage obtained in FIG. 9 is a more accurate value.

As a result, the dielectric breakdown voltage obtained in FIG. 7 may be corrected based on the dielectric breakdown voltage obtained in FIG. 9.

FIG. 10 is a graph comparing only the gate current of FIGS. 7 and 9. In FIG. 10, V _{T (Normal)} is the gate voltage at the point where tunneling starts in the gate current curve of FIG. 9, and V _{T (SOI)} is the gate voltage at the point where tunneling starts in the gate current curve of FIG. 7.

Where the correction factor C _eff is

C _eff = V _{T (Normal)} / V _{T (SOI)}

The effective electric field (E _OX-eff ) applied to the gate insulating film 314 is when the thickness of the gate insulating film 314 is T _OX ,

E _OX-eff = C _eff (V _OX / T _OX )

It can be represented by. Therefore, if the dielectric breakdown voltage of the gate insulating film measured on the silicon double film wafer _is called V _{B (SOI)} , and the corrected dielectric breakdown voltage of the gate insulating film is V _{B (eff)} ,

V _{B (eff)} = C _eff × V _{B (SOI)}

to be.

Thus, correcting the dielectric breakdown voltage can be obtained by correcting the dielectric breakdown voltage of the gate insulating film obtained in the electrode breakdown voltage measuring electrode structure formed according to the embodiment of the present invention using the correction factor.

According to the present invention, an electrode for measuring the breakdown voltage of the gate insulating layer can be formed by omitting processes such as ion implantation and diffusion.

Claims (5)

Silicon base substrate, An insulating oxide film formed on the base substrate, A silicon thin film formed on the insulating oxide film, A gate insulating film formed on the silicon thin film and having a contact hole for exposing the silicon thin film; A gate electrode formed on the gate insulating film, A source electrode and a drain electrode formed on the gate insulating layer and connected to the silicon thin film through the contact hole, respectively. Including, The silicon thin film is an electrode for dielectric breakdown voltage measurement of a silicon double film wafer doped with one or less kinds of impurities. In claim 1, And an isolation oxide layer separating the silicon thin film into a plurality of isolated regions. A first step of measuring the dielectric breakdown voltage of the gate insulating film using the dielectric breakdown voltage measuring electrode of the silicon double film wafer of claim 1, Except for the absence of the insulating oxide film and the silicon thin film, the dielectric breakdown of the gate insulating film using the dielectric breakdown voltage measurement electrode of the silicon single layer wafer having the same structure as the electrode for the dielectric breakdown voltage measurement of the silicon double layer wafer The second step of measuring the voltage, Correcting the dielectric breakdown voltage of the gate insulating film measured in the first step based on the dielectric breakdown voltage of the gate insulating film measured in the second step. Method for measuring the dielectric breakdown voltage of a silicon double film wafer comprising a. In claim 3, And a thickness of the gate insulating film of the silicon double film wafer and the gate insulating film of the silicon single film wafer is 18 nm. The method of claim 3 or 4, When the voltage at which tunneling starts in the gate insulating film of the silicon double layer wafer is called V _{T (SOI)} , and the voltage at which tunneling starts in the gate insulating film of the silicon single layer wafer _is called V _{T (Normal)} , C _eff = V _{T (Normal)} / V _{T (SOI)} , and the dielectric breakdown voltage of the gate insulating film measured on the silicon double film wafer _is called V _{B (SOI)} , and the dielectric breakdown voltage of the corrected gate insulating film is V _{B (eff).} In this case, the step of correcting the dielectric breakdown voltage is a step of substituting the value of V _{B (SOI) into} the formula of V _{B ( eff)} = C _eff × V _{B (SOI )} to obtain V _{B (eff)} . Method for measuring the breakdown voltage of a wafer.